diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec13dd3..9fdce1d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,12 @@
 
 This is the changelog for the open source version of tiktoken.
 
+## [v0.10.0]
+
+- Support for gpt-4.1 and gpt-4.5 models
+
 ## [v0.9.0]
+
 - Support for `o1` and `o3` models
 - Better error messages when loading invalid vocabulary files
 - Support for encoding to numpy arrays
diff --git a/tests/test_misc.py b/tests/test_misc.py
index 7da5389..01f7f03 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -15,8 +15,17 @@ def test_encoding_for_model():
     assert enc.name == "cl100k_base"
     enc = tiktoken.encoding_for_model("gpt-4")
     assert enc.name == "cl100k_base"
-    enc = tiktoken.encoding_for_model("gpt-4o")
-    assert enc.name == "o200k_base"
+
+    for model in [
+        "gpt-4o",
+        "gpt-4o-mini",
+        "gpt-4.1",
+        "gpt-4.1-mini",
+        "gpt-4.1-nano",
+        "gpt-4.5-preview",
+    ]:
+        enc = tiktoken.encoding_for_model(model)
+        assert enc.name == "o200k_base", f"{model} should use o200k_base"
 
 
 def test_optional_blobfile_dependency():
diff --git a/tiktoken/model.py b/tiktoken/model.py
index 4298ae7..a96cc9e 100644
--- a/tiktoken/model.py
+++ b/tiktoken/model.py
@@ -11,6 +11,8 @@
     "chatgpt-4o-": "o200k_base",
     "gpt-4o-": "o200k_base",  # e.g., gpt-4o-2024-05-13
     "gpt-4-": "cl100k_base",  # e.g., gpt-4-0314, etc., plus gpt-4-32k
+    "gpt-4.1-": "o200k_base",  # e.g., gpt-4.1-nano, gpt-4.1-mini
+    "gpt-4.5-": "o200k_base", # e.g., gpt-4.5-preview
     "gpt-3.5-turbo-": "cl100k_base",  # e.g, gpt-3.5-turbo-0301, -0401, etc.
     "gpt-35-turbo-": "cl100k_base",  # Azure deployment name
     # fine-tuned
@@ -28,6 +30,8 @@
     # chat
     "gpt-4o": "o200k_base",
     "gpt-4": "cl100k_base",
+    "gpt-4.1": "o200k_base",
+    "gpt-4.5": "o200k_base",
     "gpt-3.5-turbo": "cl100k_base",
     "gpt-3.5": "cl100k_base",  # Common shorthand
     "gpt-35-turbo": "cl100k_base",  # Azure deployment name