diff --git a/changes/3004.feature.rst b/changes/3004.feature.rst
new file mode 100644
index 0000000000..b15a5ec943
--- /dev/null
+++ b/changes/3004.feature.rst
@@ -0,0 +1,3 @@
+Optimizes reading more than one, but not all, chunks from a shard. Chunks are now read in parallel
+and reads of nearby chunks within the same shard are combined to reduce the number of calls to the store.
+See :ref:`user-guide-config` for more details.
\ No newline at end of file
diff --git a/docs/user-guide/config.rst b/docs/user-guide/config.rst
index 0ae8017ca9..78acf9f331 100644
--- a/docs/user-guide/config.rst
+++ b/docs/user-guide/config.rst
@@ -33,6 +33,10 @@ Configuration options include the following:
 - Async and threading options, e.g. ``async.concurrency`` and ``threading.max_workers``
 - Selections of implementations of codecs, codec pipelines and buffers
 - Enabling GPU support with ``zarr.config.enable_gpu()``. See :ref:`user-guide-gpu` for more.
+- Tuning reads from sharded zarrs. When reading less than a complete shard, reads of nearby chunks
+  within the same shard will be combined into a single request if they are less than
+  ``sharding.read.coalesce_max_gap_bytes`` apart and the combined request size is less than
+  ``sharding.read.coalesce_max_bytes``.
 
 For selecting custom implementations of codecs, pipelines, buffers and ndbuffers,
 first register the implementations in the registry and then select them in the config.
@@ -61,4 +65,6 @@ This is the current default configuration::
    'default_zarr_format': 3,
    'json_indent': 2,
    'ndbuffer': 'zarr.buffer.cpu.NDBuffer',
-   'threading': {'max_workers': None}}
+   'sharding': {'read': {'coalesce_max_bytes': 104857600,
+                         'coalesce_max_gap_bytes': 1048576}},
+   'threading': {'max_workers': None}}
\ No newline at end of file
diff --git a/src/zarr/codecs/sharding.py b/src/zarr/codecs/sharding.py
index cd8676b4d1..b29e24cfb9 100644
--- a/src/zarr/codecs/sharding.py
+++ b/src/zarr/codecs/sharding.py
@@ -38,11 +38,13 @@
 from zarr.core.common import (
     ChunkCoords,
     ChunkCoordsLike,
+    concurrent_map,
     parse_enum,
     parse_named_configuration,
     parse_shapelike,
     product,
 )
+from zarr.core.config import config
 from zarr.core.dtype.npy.int import UInt64
 from zarr.core.indexing import (
     BasicIndexer,
@@ -198,7 +200,9 @@ async def from_bytes(
 
     @classmethod
     def create_empty(
-        cls, chunks_per_shard: ChunkCoords, buffer_prototype: BufferPrototype | None = None
+        cls,
+        chunks_per_shard: ChunkCoords,
+        buffer_prototype: BufferPrototype | None = None,
     ) -> _ShardReader:
         if buffer_prototype is None:
             buffer_prototype = default_buffer_prototype()
@@ -248,7 +252,9 @@ def merge_with_morton_order(
 
     @classmethod
     def create_empty(
-        cls, chunks_per_shard: ChunkCoords, buffer_prototype: BufferPrototype | None = None
+        cls,
+        chunks_per_shard: ChunkCoords,
+        buffer_prototype: BufferPrototype | None = None,
     ) -> _ShardBuilder:
         if buffer_prototype is None:
             buffer_prototype = default_buffer_prototype()
@@ -329,9 +335,18 @@ async def finalize(
         return await shard_builder.finalize(index_location, index_encoder)
 
 
+class _ChunkCoordsByteSlice(NamedTuple):
+    """Holds a chunk's coordinates and its byte range in a serialized shard."""
+
+    coords: ChunkCoords
+    byte_slice: slice
+
+
 @dataclass(frozen=True)
 class ShardingCodec(
-    ArrayBytesCodec, ArrayBytesCodecPartialDecodeMixin, ArrayBytesCodecPartialEncodeMixin
+    ArrayBytesCodec,
+    ArrayBytesCodecPartialDecodeMixin,
+    ArrayBytesCodecPartialEncodeMixin,
 ):
     chunk_shape: ChunkCoords
     codecs: tuple[Codec, ...]
@@ -508,32 +523,21 @@ async def _decode_partial_single(
         all_chunk_coords = {chunk_coords for chunk_coords, *_ in indexed_chunks}
 
         # reading bytes of all requested chunks
-        shard_dict: ShardMapping = {}
+        shard_dict_maybe: ShardMapping | None = {}
         if self._is_total_shard(all_chunk_coords, chunks_per_shard):
             # read entire shard
             shard_dict_maybe = await self._load_full_shard_maybe(
-                byte_getter=byte_getter,
-                prototype=chunk_spec.prototype,
-                chunks_per_shard=chunks_per_shard,
+                byte_getter, chunk_spec.prototype, chunks_per_shard
             )
-            if shard_dict_maybe is None:
-                return None
-            shard_dict = shard_dict_maybe
         else:
             # read some chunks within the shard
-            shard_index = await self._load_shard_index_maybe(byte_getter, chunks_per_shard)
-            if shard_index is None:
-                return None
-            shard_dict = {}
-            for chunk_coords in all_chunk_coords:
-                chunk_byte_slice = shard_index.get_chunk_slice(chunk_coords)
-                if chunk_byte_slice:
-                    chunk_bytes = await byte_getter.get(
-                        prototype=chunk_spec.prototype,
-                        byte_range=RangeByteRequest(chunk_byte_slice[0], chunk_byte_slice[1]),
-                    )
-                    if chunk_bytes:
-                        shard_dict[chunk_coords] = chunk_bytes
+            shard_dict_maybe = await self._load_partial_shard_maybe(
+                byte_getter, chunk_spec.prototype, chunks_per_shard, all_chunk_coords
+            )
+
+        if shard_dict_maybe is None:
+            return None
+        shard_dict = shard_dict_maybe
 
         # decoding chunks and writing them into the output buffer
         await self.codec_pipeline.read(
@@ -615,7 +619,9 @@ async def _encode_partial_single(
 
         indexer = list(
             get_indexer(
-                selection, shape=shard_shape, chunk_grid=RegularChunkGrid(chunk_shape=chunk_shape)
+                selection,
+                shape=shard_shape,
+                chunk_grid=RegularChunkGrid(chunk_shape=chunk_shape),
             )
         )
 
@@ -689,7 +695,8 @@ def _shard_index_size(self, chunks_per_shard: ChunkCoords) -> int:
             get_pipeline_class()
             .from_codecs(self.index_codecs)
             .compute_encoded_size(
-                16 * product(chunks_per_shard), self._get_index_chunk_spec(chunks_per_shard)
+                16 * product(chunks_per_shard),
+                self._get_index_chunk_spec(chunks_per_shard),
             )
         )
 
@@ -734,7 +741,8 @@ async def _load_shard_index_maybe(
             )
         else:
             index_bytes = await byte_getter.get(
-                prototype=numpy_buffer_prototype(), byte_range=SuffixByteRequest(shard_index_size)
+                prototype=numpy_buffer_prototype(),
+                byte_range=SuffixByteRequest(shard_index_size),
             )
         if index_bytes is not None:
             return await self._decode_shard_index(index_bytes, chunks_per_shard)
@@ -748,7 +756,10 @@ async def _load_shard_index(
         ) or _ShardIndex.create_empty(chunks_per_shard)
 
     async def _load_full_shard_maybe(
-        self, byte_getter: ByteGetter, prototype: BufferPrototype, chunks_per_shard: ChunkCoords
+        self,
+        byte_getter: ByteGetter,
+        prototype: BufferPrototype,
+        chunks_per_shard: ChunkCoords,
     ) -> _ShardReader | None:
         shard_bytes = await byte_getter.get(prototype=prototype)
 
@@ -758,6 +769,115 @@ async def _load_full_shard_maybe(
             else None
         )
 
+    async def _load_partial_shard_maybe(
+        self,
+        byte_getter: ByteGetter,
+        prototype: BufferPrototype,
+        chunks_per_shard: ChunkCoords,
+        all_chunk_coords: set[ChunkCoords],
+    ) -> ShardMapping | None:
+        """
+        Read chunks from `byte_getter` for the case where the read is less than a full shard.
+        Returns a mapping of chunk coordinates to bytes or None.
+        """
+        shard_index = await self._load_shard_index_maybe(byte_getter, chunks_per_shard)
+        if shard_index is None:
+            return None
+
+        chunks = [
+            _ChunkCoordsByteSlice(chunk_coords, slice(*chunk_byte_slice))
+            for chunk_coords in all_chunk_coords
+            # Drop chunks where index lookup fails
+            # e.g. empty chunks when write_empty_chunks = False
+            if (chunk_byte_slice := shard_index.get_chunk_slice(chunk_coords))
+        ]
+
+        groups = self._coalesce_chunks(chunks)
+
+        shard_dicts = await concurrent_map(
+            [(group, byte_getter, prototype) for group in groups],
+            self._get_group_bytes,
+            config.get("async.concurrency"),
+        )
+
+        shard_dict: ShardMutableMapping = {}
+        for d in shard_dicts:
+            if d is None:
+                return None
+            shard_dict.update(d)
+
+        return shard_dict
+
+    def _coalesce_chunks(
+        self,
+        chunks: list[_ChunkCoordsByteSlice],
+    ) -> list[list[_ChunkCoordsByteSlice]]:
+        """
+        Combine chunks from a single shard into groups that should be read together
+        in a single request to the store.
+
+        Respects the following configuration options:
+        - `sharding.read.coalesce_max_gap_bytes`: The maximum gap between
+          chunks to coalesce into a single group.
+        - `sharding.read.coalesce_max_bytes`: The maximum number of bytes in a group.
+        """
+        max_gap_bytes = config.get("sharding.read.coalesce_max_gap_bytes")
+        coalesce_max_bytes = config.get("sharding.read.coalesce_max_bytes")
+
+        sorted_chunks = sorted(chunks, key=lambda c: c.byte_slice.start)
+
+        if len(sorted_chunks) == 0:
+            return []
+
+        groups = []
+        current_group = [sorted_chunks[0]]
+
+        for chunk in sorted_chunks[1:]:
+            gap_to_chunk = chunk.byte_slice.start - current_group[-1].byte_slice.stop
+            size_if_coalesced = chunk.byte_slice.stop - current_group[0].byte_slice.start
+            if gap_to_chunk < max_gap_bytes and size_if_coalesced < coalesce_max_bytes:
+                current_group.append(chunk)
+            else:
+                groups.append(current_group)
+                current_group = [chunk]
+
+        groups.append(current_group)
+
+        return groups
+
+    async def _get_group_bytes(
+        self,
+        group: list[_ChunkCoordsByteSlice],
+        byte_getter: ByteGetter,
+        prototype: BufferPrototype,
+    ) -> ShardMapping | None:
+        """
+        Reads a possibly coalesced group of one or more chunks from a shard.
+        Returns a mapping of chunk coordinates to bytes.
+        """
+        # _coalesce_chunks ensures that the group is not empty.
+        group_start = group[0].byte_slice.start
+        group_end = group[-1].byte_slice.stop
+
+        # A single call to retrieve the bytes for the entire group.
+        group_bytes = await byte_getter.get(
+            prototype=prototype,
+            byte_range=RangeByteRequest(group_start, group_end),
+        )
+        if group_bytes is None:
+            return None
+
+        # Extract the bytes corresponding to each chunk in group from group_bytes.
+        shard_dict = {}
+        for chunk in group:
+            chunk_slice = slice(
+                chunk.byte_slice.start - group_start,
+                chunk.byte_slice.stop - group_start,
+            )
+            shard_dict[chunk.coords] = group_bytes[chunk_slice]
+
+        return shard_dict
+
     def compute_encoded_size(self, input_byte_length: int, shard_spec: ArraySpec) -> int:
         chunks_per_shard = self._get_chunks_per_shard(shard_spec)
         return input_byte_length + self._shard_index_size(chunks_per_shard)
diff --git a/src/zarr/core/config.py b/src/zarr/core/config.py
index cc3c33cd17..6dd2bc3e5b 100644
--- a/src/zarr/core/config.py
+++ b/src/zarr/core/config.py
@@ -109,6 +109,12 @@ def enable_gpu(self) -> ConfigSet:
             },
             "async": {"concurrency": 10, "timeout": None},
             "threading": {"max_workers": None},
+            "sharding": {
+                "read": {
+                    "coalesce_max_bytes": 100 * 2**20,  # 100MiB
+                    "coalesce_max_gap_bytes": 2**20,  # 1MiB
+                }
+            },
             "json_indent": 2,
             "codec_pipeline": {
                 "path": "zarr.core.codec_pipeline.BatchedCodecPipeline",
diff --git a/tests/test_codecs/test_sharding.py b/tests/test_codecs/test_sharding.py
index 403fd80e81..f124e14675 100644
--- a/tests/test_codecs/test_sharding.py
+++ b/tests/test_codecs/test_sharding.py
@@ -1,5 +1,6 @@
 import pickle
 from typing import Any
+from unittest.mock import AsyncMock
 
 import numpy as np
 import numpy.typing as npt
@@ -9,7 +10,7 @@
 import zarr.api
 import zarr.api.asynchronous
 from zarr import Array
-from zarr.abc.store import Store
+from zarr.abc.store import RangeByteRequest, Store, SuffixByteRequest
 from zarr.codecs import (
     BloscCodec,
     ShardingCodec,
@@ -110,7 +111,9 @@ def test_sharding_scalar(
     indirect=["array_fixture"],
 )
 def test_sharding_partial(
-    store: Store, array_fixture: npt.NDArray[Any], index_location: ShardingCodecIndexLocation
+    store: Store,
+    array_fixture: npt.NDArray[Any],
+    index_location: ShardingCodecIndexLocation,
 ) -> None:
     data = array_fixture
     spath = StorePath(store)
@@ -146,7 +149,9 @@ def test_sharding_partial(
     indirect=["array_fixture"],
 )
 def test_sharding_partial_readwrite(
-    store: Store, array_fixture: npt.NDArray[Any], index_location: ShardingCodecIndexLocation
+    store: Store,
+    array_fixture: npt.NDArray[Any],
+    index_location: ShardingCodecIndexLocation,
 ) -> None:
     data = array_fixture
     spath = StorePath(store)
@@ -178,7 +183,9 @@ def test_sharding_partial_readwrite(
 @pytest.mark.parametrize("index_location", ["start", "end"])
 @pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
 def test_sharding_partial_read(
-    store: Store, array_fixture: npt.NDArray[Any], index_location: ShardingCodecIndexLocation
+    store: Store,
+    array_fixture: npt.NDArray[Any],
+    index_location: ShardingCodecIndexLocation,
 ) -> None:
     data = array_fixture
     spath = StorePath(store)
@@ -197,6 +204,301 @@ def test_sharding_partial_read(
     assert np.all(read_data == 1)
 
 
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+@pytest.mark.parametrize("coalesce_reads", [True, False])
+def test_sharding_multiple_chunks_partial_shard_read(
+    store: Store, index_location: ShardingCodecIndexLocation, coalesce_reads: bool
+) -> None:
+    array_shape = (16, 64)
+    shard_shape = (8, 32)
+    chunk_shape = (2, 4)
+    data = np.arange(np.prod(array_shape), dtype="float32").reshape(array_shape)
+
+    if coalesce_reads:
+        # 1MiB, enough to coalesce all chunks within a shard in this example
+        zarr.config.set({"sharding.read.coalesce_max_gap_bytes": 2**20})
+    else:
+        # disable coalescing
+        zarr.config.set({"sharding.read.coalesce_max_gap_bytes": -1})
+
+    store_mock = AsyncMock(wraps=store, spec=store.__class__)
+    a = zarr.create_array(
+        StorePath(store_mock),
+        shape=data.shape,
+        chunks=chunk_shape,
+        shards={"shape": shard_shape, "index_location": index_location},
+        compressors=BloscCodec(cname="lz4"),
+        dtype=data.dtype,
+        fill_value=1,
+    )
+    a[:] = data
+
+    store_mock.reset_mock()  # ignore store calls during array creation
+
+    # Reads 3 (2 full, 1 partial) chunks each from 2 shards (a subset of both shards)
+    # for a total of 6 chunks accessed
+    assert np.allclose(a[0, 22:42], np.arange(22, 42, dtype="float32"))
+
+    if coalesce_reads:
+        # 2 shard index requests + 2 coalesced chunk data byte ranges (one for each shard)
+        assert store_mock.get.call_count == 4
+    else:
+        # 2 shard index requests + 6 chunks
+        assert store_mock.get.call_count == 8
+
+    for method, args, kwargs in store_mock.method_calls:
+        assert method == "get"
+        assert args[0].startswith("c/")  # get from a chunk
+        assert isinstance(kwargs["byte_range"], (SuffixByteRequest, RangeByteRequest))
+
+    store_mock.reset_mock()
+
+    # Reads 4 chunks from both shards along dimension 0 for a total of 8 chunks accessed
+    assert np.allclose(a[:, 0], np.arange(0, data.size, array_shape[1], dtype="float32"))
+
+    if coalesce_reads:
+        # 2 shard index requests + 2 coalesced chunk data byte ranges (one for each shard)
+        assert store_mock.get.call_count == 4
+    else:
+        # 2 shard index requests + 8 chunks
+        assert store_mock.get.call_count == 10
+
+    for method, args, kwargs in store_mock.method_calls:
+        assert method == "get"
+        assert args[0].startswith("c/")  # get from a chunk
+        assert isinstance(kwargs["byte_range"], (SuffixByteRequest, RangeByteRequest))
+
+
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+@pytest.mark.parametrize("coalesce_reads", [True, False])
+def test_sharding_duplicate_read_indexes(
+    store: Store, index_location: ShardingCodecIndexLocation, coalesce_reads: bool
+) -> None:
+    """
+    Check that coalesce optimization parses the grouped reads back out correctly
+    when there are multiple reads for the same index.
+    """
+    array_shape = (15,)
+    shard_shape = (8,)
+    chunk_shape = (2,)
+    data = np.arange(np.prod(array_shape), dtype="float32").reshape(array_shape)
+
+    if coalesce_reads:
+        # 1MiB, enough to coalesce all chunks within a shard in this example
+        zarr.config.set({"sharding.read.coalesce_max_gap_bytes": 2**20})
+    else:
+        # disable coalescing
+        zarr.config.set({"sharding.read.coalesce_max_gap_bytes": -1})
+
+    store_mock = AsyncMock(wraps=store, spec=store.__class__)
+    a = zarr.create_array(
+        StorePath(store_mock),
+        shape=data.shape,
+        chunks=chunk_shape,
+        shards={"shape": shard_shape, "index_location": index_location},
+        compressors=BloscCodec(cname="lz4"),
+        dtype=data.dtype,
+        fill_value=-1,
+    )
+    a[:] = data
+
+    store_mock.reset_mock()  # ignore store calls during array creation
+
+    # Read the same index multiple times, do that from two chunks which can be coalesced
+    indexer = [8, 8, 12, 12]
+    np.array_equal(a[indexer], data[indexer])
+
+    if coalesce_reads:
+        # 1 shard index request + 1 coalesced read
+        assert store_mock.get.call_count == 2
+    else:
+        # 1 shard index request + 2 chunks
+        assert store_mock.get.call_count == 3
+
+
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+def test_sharding_read_empty_chunks_within_non_empty_shard_write_empty_false(
+    store: Store, index_location: ShardingCodecIndexLocation
+) -> None:
+    """
+    Case where
+        - some, but not all, chunks in the last shard are empty
+        - the last shard is not complete (array length is not a multiple of shard shape),
+          this takes us down the partial shard read path
+        - write_empty_chunks=False so the shard index will have fewer entries than chunks in the shard
+    """
+    # array with mixed empty and non-empty chunks in second shard
+    data = np.array([
+        # shard 0. full 8 elements, all chunks have some non-fill data
+        0, 1, 2, 3, 4, 5, 6, 7,
+        # shard 1. 6 elements (< shard shape)
+         2,  0, # chunk 0, written
+        -9, -9, # chunk 1, all fill, not written
+         4,  5  # chunk 2, written
+    ], dtype="int32")  # fmt: off
+
+    spath = StorePath(store)
+    a = zarr.create_array(
+        spath,
+        shape=(14,),
+        chunks=(2,),
+        shards={"shape": (8,), "index_location": index_location},
+        dtype="int32",
+        fill_value=-9,
+        filters=None,
+        compressors=None,
+        config={"write_empty_chunks": False},
+    )
+    a[:] = data
+
+    assert np.array_equal(a[:], data)
+
+
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+def test_sharding_read_empty_chunks_within_empty_shard_write_empty_false(
+    store: Store, index_location: ShardingCodecIndexLocation
+) -> None:
+    """
+    Case where
+        - all chunks in last shard are empty
+        - the last shard is not complete (array length is not a multiple of shard shape),
+          this takes us down the partial shard read path
+        - write_empty_chunks=False so the shard index will have no entries
+    """
+    fill_value = -99
+    shard_size = 8
+    data = np.arange(14, dtype="int32")
+    data[shard_size:] = fill_value  # 2nd shard is all fill value
+
+    spath = StorePath(store)
+    a = zarr.create_array(
+        spath,
+        shape=(14,),
+        chunks=(2,),
+        shards={"shape": (shard_size,), "index_location": index_location},
+        dtype="int32",
+        fill_value=fill_value,
+        filters=None,
+        compressors=None,
+        config={"write_empty_chunks": False},
+    )
+    a[:] = data
+
+    assert np.array_equal(a[:], data)
+
+
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+def test_sharding_partial_shard_read__index_load_fails(
+    store: Store, index_location: ShardingCodecIndexLocation
+) -> None:
+    """Test fill value is returned when the call to the store to load the bytes of the shard's chunk index fails."""
+    array_shape = (16,)
+    shard_shape = (16,)
+    chunk_shape = (8,)
+    data = np.arange(np.prod(array_shape), dtype="float32").reshape(array_shape)
+    fill_value = -999
+
+    store_mock = AsyncMock(wraps=store, spec=store.__class__)
+    # loading the index is the first call to .get() so returning None will simulate an index load failure
+    store_mock.get.return_value = None
+
+    a = zarr.create_array(
+        StorePath(store_mock),
+        shape=data.shape,
+        chunks=chunk_shape,
+        shards={"shape": shard_shape, "index_location": index_location},
+        compressors=BloscCodec(cname="lz4"),
+        dtype=data.dtype,
+        fill_value=fill_value,
+    )
+    a[:] = data
+
+    # Read from one of two chunks in a shard to test the partial shard read path
+    assert a[0] == fill_value
+    assert a[0] != data[0]
+
+
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+def test_sharding_partial_shard_read__index_chunk_slice_fails(
+    store: Store,
+    index_location: ShardingCodecIndexLocation,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test fill value is returned when looking up a chunk's byte slice within a shard fails."""
+    array_shape = (16,)
+    shard_shape = (16,)
+    chunk_shape = (8,)
+    data = np.arange(np.prod(array_shape), dtype="float32").reshape(array_shape)
+    fill_value = -999
+
+    monkeypatch.setattr(
+        "zarr.codecs.sharding._ShardIndex.get_chunk_slice",
+        lambda self, chunk_coords: None,
+    )
+
+    a = zarr.create_array(
+        StorePath(store),
+        shape=data.shape,
+        chunks=chunk_shape,
+        shards={"shape": shard_shape, "index_location": index_location},
+        compressors=BloscCodec(cname="lz4"),
+        dtype=data.dtype,
+        fill_value=fill_value,
+    )
+    a[:] = data
+
+    # Read from one of two chunks in a shard to test the partial shard read path
+    assert a[0] == fill_value
+    assert a[0] != data[0]
+
+
+@pytest.mark.parametrize("index_location", ["start", "end"])
+@pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
+def test_sharding_partial_shard_read__chunk_load_fails(
+    store: Store, index_location: ShardingCodecIndexLocation
+) -> None:
+    """Test fill value is returned when the call to the store to load a chunk's bytes fails."""
+    array_shape = (16,)
+    shard_shape = (16,)
+    chunk_shape = (8,)
+    data = np.arange(np.prod(array_shape), dtype="float32").reshape(array_shape)
+    fill_value = -999
+
+    store_mock = AsyncMock(wraps=store, spec=store.__class__)
+
+    a = zarr.create_array(
+        StorePath(store_mock),
+        shape=data.shape,
+        chunks=chunk_shape,
+        shards={"shape": shard_shape, "index_location": index_location},
+        compressors=BloscCodec(cname="lz4"),
+        dtype=data.dtype,
+        fill_value=fill_value,
+    )
+    a[:] = data
+
+    # Set up store mock after array creation to only modify calls during array indexing
+    # Succeed on first call (index load), fail on subsequent calls (chunk loads)
+    async def first_success_then_fail(*args: Any, **kwargs: Any) -> Any:
+        if store_mock.get.call_count == 1:
+            return await store.get(*args, **kwargs)
+        else:
+            return None
+
+    store_mock.get.reset_mock()
+    store_mock.get.side_effect = first_success_then_fail
+
+    # Read from one of two chunks in a shard to test the partial shard read path
+    assert a[0] == fill_value
+    assert a[0] != data[0]
+
+
 @pytest.mark.parametrize(
     "array_fixture",
     [
@@ -207,7 +509,9 @@ def test_sharding_partial_read(
 @pytest.mark.parametrize("index_location", ["start", "end"])
 @pytest.mark.parametrize("store", ["local", "memory", "zip"], indirect=["store"])
 def test_sharding_partial_overwrite(
-    store: Store, array_fixture: npt.NDArray[Any], index_location: ShardingCodecIndexLocation
+    store: Store,
+    array_fixture: npt.NDArray[Any],
+    index_location: ShardingCodecIndexLocation,
 ) -> None:
     data = array_fixture[:10, :10, :10]
     spath = StorePath(store)
@@ -320,7 +624,6 @@ def test_nested_sharding_create_array(
         filters=None,
         compressors=None,
     )
-    print(a.metadata.to_dict())
 
     a[:, :, :] = data
 
@@ -380,7 +683,6 @@ async def test_delete_empty_shards(store: Store) -> None:
         compressors=None,
         fill_value=1,
     )
-    print(a.metadata.to_dict())
     await _AsyncArrayProxy(a)[:, :].set(np.zeros((16, 16)))
     await _AsyncArrayProxy(a)[8:, :].set(np.ones((8, 16)))
     await _AsyncArrayProxy(a)[:, 8:].set(np.ones((16, 8)))
@@ -425,7 +727,6 @@ async def test_sharding_with_empty_inner_chunk(
     )
     data[:4, :4] = fill_value
     await a.setitem(..., data)
-    print("read data")
     data_read = await a.getitem(...)
     assert np.array_equal(data_read, data)
 
@@ -437,7 +738,9 @@ async def test_sharding_with_empty_inner_chunk(
 )
 @pytest.mark.parametrize("chunks_per_shard", [(5, 2), (2, 5), (5, 5)])
 async def test_sharding_with_chunks_per_shard(
-    store: Store, index_location: ShardingCodecIndexLocation, chunks_per_shard: tuple[int]
+    store: Store,
+    index_location: ShardingCodecIndexLocation,
+    chunks_per_shard: tuple[int],
 ) -> None:
     chunk_shape = (2, 1)
     shape = tuple(x * y for x, y in zip(chunks_per_shard, chunk_shape, strict=False))
diff --git a/tests/test_config.py b/tests/test_config.py
index da5b2cc488..3355c9d744 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -75,6 +75,12 @@ def test_config_defaults_set() -> None:
                 },
                 "buffer": "zarr.buffer.cpu.Buffer",
                 "ndbuffer": "zarr.buffer.cpu.NDBuffer",
+                "sharding": {
+                    "read": {
+                        "coalesce_max_bytes": 100 * 2**20,  # 100 MiB
+                        "coalesce_max_gap_bytes": 2**20,  # 1 MiB
+                    }
+                },
             }
         ]
     )
@@ -83,6 +89,8 @@ def test_config_defaults_set() -> None:
     assert config.get("async.timeout") is None
     assert config.get("codec_pipeline.batch_size") == 1
     assert config.get("json_indent") == 2
+    assert config.get("sharding.read.coalesce_max_bytes") == 100 * 2**20  # 100 MiB
+    assert config.get("sharding.read.coalesce_max_gap_bytes") == 2**20  # 1 MiB
 
 
 @pytest.mark.parametrize(