diff --git a/tests/test_hackertarget_apikey.py b/tests/test_hackertarget_apikey.py
new file mode 100644
index 00000000000..3f22923561b
--- /dev/null
+++ b/tests/test_hackertarget_apikey.py
@@ -0,0 +1,50 @@
+import requests
+from theHarvester.discovery import hackertarget as ht_mod
+
+class DummyResp:
+    def __init__(self, text, status_code=200):
+        self.text = text
+        self.status_code = status_code
+    def raise_for_status(self):
+        if self.status_code != 200:
+            raise requests.HTTPError()
+
+def test_append_apikey_to_url():
+    base = "https://api.hackertarget.com/hostsearch/?q=example.com"
+    out = ht_mod._append_apikey_to_url(base, "MYKEY")
+    assert "apikey=MYKEY" in out
+
+def test_do_search_with_apikey(monkeypatch):
+    # make _get_hackertarget_key return a known key
+    monkeypatch.setattr(ht_mod, "_get_hackertarget_key", lambda: "TESTKEY")
+
+    # monkeypatch AsyncFetcher.fetch_all to capture requested URLs
+    async def fake_fetch_all(urls, headers=None, proxy=False):
+        # ensure apikey present in each URL
+        assert all(("apikey=TESTKEY" in u or "apikey=TESTKEY" in (u.split("?", 1)[1] if "?" in u else "")) for u in urls)
+        return ["1.2.3.4,host.example.com\n", "No PTR records found\n"]
+
+    monkeypatch.setattr(ht_mod.AsyncFetcher, "fetch_all", fake_fetch_all)
+
+    s = ht_mod.SearchHackerTarget("example.com")
+
+    # run the coroutine
+    import asyncio
+    asyncio.get_event_loop().run_until_complete(s.do_search())
+
+    # after do_search, total_results should include our fake response (commas replaced by colons)
+    assert "1.2.3.4:host.example.com" in s.total_results
+
+def test_do_search_without_apikey(monkeypatch):
+    monkeypatch.setattr(ht_mod, "_get_hackertarget_key", lambda: None)
+
+    async def fake_fetch_all(urls, headers=None, proxy=False):
+        assert all("apikey=" not in u for u in urls)
+        return ["1.2.3.4,host.example.com\n"]
+
+    monkeypatch.setattr(ht_mod.AsyncFetcher, "fetch_all", fake_fetch_all)
+
+    s = ht_mod.SearchHackerTarget("example.com")
+    import asyncio
+    asyncio.get_event_loop().run_until_complete(s.do_search())
+    assert "1.2.3.4:host.example.com" in s.total_results
diff --git a/theHarvester/discovery/hackertarget.py b/theHarvester/discovery/hackertarget.py
index b440392856c..6b8741c763f 100644
--- a/theHarvester/discovery/hackertarget.py
+++ b/theHarvester/discovery/hackertarget.py
@@ -1,9 +1,108 @@
+# theHarvester/discovery/hackertarget.py
+import os
+from urllib.parse import parse_qsl, urlencode, urlsplit, urlunsplit
+
+# yaml is optional; fall back gracefully if not installed
+try:
+    import yaml
+except Exception:
+    yaml = None
+
 from theHarvester.lib.core import AsyncFetcher, Core
 
 
+def _append_apikey_to_url(url: str, apikey: str | None) -> str:
+    """
+    Safely append an `apikey` query parameter to a URL, preserving existing params.
+    If apikey is falsy, returns the original URL unchanged.
+    """
+    if not apikey:
+        return url
+    scheme, netloc, path, query, fragment = urlsplit(url)
+    q = dict(parse_qsl(query))
+    q['apikey'] = apikey
+    new_query = urlencode(q)
+    return urlunsplit((scheme, netloc, path, new_query, fragment))
+
+
+def _load_api_keys_fallback() -> dict:
+    """
+    Fallback loader for api-keys.yml if the project does not provide a loader.
+    Looks in a few likely paths and returns a dict (or {}).
+    """
+    if yaml is None:
+        return {}
+
+    candidates = [
+        os.path.join(os.getcwd(), 'api-keys.yml'),
+        os.path.join(os.getcwd(), 'theHarvester', 'api-keys.yml'),
+        os.path.join(os.getcwd(), 'theHarvester', 'etc', 'api-keys.yml'),
+        os.path.expanduser('~/.theHarvester/api-keys.yml'),
+    ]
+
+    for p in candidates:
+        if os.path.isfile(p):
+            try:
+                with open(p, encoding='utf-8') as fh:
+                    return yaml.safe_load(fh) or {}
+            except (OSError, yaml.YAMLError):
+                # treat read/parse errors as "no keys found" for this fallback
+                return {}
+    return {}
+
+
+def _get_hackertarget_key() -> str | None:
+    """
+    Try to obtain Hackertarget API key from repo-provided loader (preferred),
+    or fall back to reading api-keys.yml directly.
+
+    Accepts multiple common formats:
+      hackertarget: "KEY"
+      hackertarget:
+        key: "KEY"
+        apikey: "KEY"
+    Also supports top-level names like hackertarget_key or hackertarget_apikey.
+    """
+    # 1) Try to use a Core loader if it exists
+    try:
+        # Many modules expose config/loaders on Core; try common names:
+        if hasattr(Core, 'load_api_keys'):
+            keys = Core.load_api_keys()
+        elif hasattr(Core, 'get_api_keys'):
+            keys = Core.get_api_keys()
+        else:
+            keys = None
+
+        if isinstance(keys, dict):
+            if 'hackertarget' in keys:
+                ht = keys['hackertarget']
+                if isinstance(ht, dict):
+                    return ht.get('key') or ht.get('apikey') or ht.get('api_key')
+                return ht
+            # other possible top-level keys
+            return keys.get('hackertarget') or keys.get('hackertarget_key') or keys.get('hackertarget_apikey')
+    except Exception:
+        # ignore and fall through to fallback loader
+        pass
+
+    # 2) Fallback: attempt to read api-keys.yml manually
+    keys = _load_api_keys_fallback()
+    if not isinstance(keys, dict):
+        return None
+    if 'hackertarget' in keys:
+        ht = keys['hackertarget']
+        if isinstance(ht, dict):
+            return ht.get('key') or ht.get('apikey') or ht.get('api_key')
+        return ht
+    return keys.get('hackertarget') or keys.get('hackertarget_key') or keys.get('hackertarget_apikey')
+
+
 class SearchHackerTarget:
     """
-    Class uses the HackerTarget api to gather subdomains and ips
+    Class uses the HackerTarget API to gather subdomains and IPs.
+
+    This version supports reading a Hackertarget API key (if present) and
+    appending it to the hackertarget request URLs as `apikey=<key>`.
     """
 
     def __init__(self, word) -> None:
@@ -15,12 +114,23 @@ def __init__(self, word) -> None:
 
     async def do_search(self) -> None:
         headers = {'User-agent': Core.get_user_agent()}
-        urls = [
+
+        # base URLs used by the original implementation
+        base_urls = [
             f'{self.hostname}/hostsearch/?q={self.word}',
             f'{self.hostname}/reversedns/?q={self.word}',
         ]
-        responses = await AsyncFetcher.fetch_all(urls, headers=headers, proxy=self.proxy)
+
+        # if user supplied an API key in api-keys.yml (or repo loader), append it
+        ht_key = _get_hackertarget_key()
+        request_urls = [_append_apikey_to_url(u, ht_key) for u in base_urls]
+
+        # fetch all using existing AsyncFetcher helper
+        responses = await AsyncFetcher.fetch_all(request_urls, headers=headers, proxy=self.proxy)
+
+        # the original code concatenated responses and replaced commas with colons
         for response in responses:
+            # response is expected to be a string; keep the original behavior
             self.total_results += response.replace(',', ':')
 
     async def process(self, proxy: bool = False) -> None: