diff --git a/.gitignore b/.gitignore
index fe8cb9f..4aac829 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,5 +14,4 @@ build/
 htmlcov/
 .claude/
 .DS_Store
-tests/
 .benchmarks/
diff --git a/src/sharpapi/_base.py b/src/sharpapi/_base.py
index 61879c2..e2c83af 100644
--- a/src/sharpapi/_base.py
+++ b/src/sharpapi/_base.py
@@ -33,6 +33,15 @@
 RETRY_MAX_DELAY = 4.0
 
 
+def normalize_base_url(base_url: str) -> str:
+    """Return the API origin URL, accepting values with a trailing /api/v1."""
+    cleaned = base_url.rstrip("/")
+    suffix = "/api/v1"
+    if cleaned.endswith(suffix):
+        return cleaned[: -len(suffix)]
+    return cleaned
+
+
 def should_retry(response: httpx.Response | None, exc: Exception | None) -> bool:
     """True for transient upstream failures worth retrying."""
     if exc is not None:
diff --git a/src/sharpapi/async_client.py b/src/sharpapi/async_client.py
index 2ba71cf..2ab8b1f 100644
--- a/src/sharpapi/async_client.py
+++ b/src/sharpapi/async_client.py
@@ -15,6 +15,7 @@
     AuthMethod,
     handle_errors,
     make_headers,
+    normalize_base_url,
     parse_rate_limit,
     parse_response,
     retry_delay,
@@ -89,7 +90,7 @@ def __init__(
 
         self._api_key = api_key
         self._auth_method: AuthMethod = auth_method
-        self._base_url = base_url.rstrip("/")
+        self._base_url = normalize_base_url(base_url)
         self._timeout = timeout
         self._http = httpx.AsyncClient(
             base_url=f"{self._base_url}/api/v1",
diff --git a/src/sharpapi/client.py b/src/sharpapi/client.py
index 9e7f9f5..4c99bf8 100644
--- a/src/sharpapi/client.py
+++ b/src/sharpapi/client.py
@@ -15,6 +15,7 @@
     AuthMethod,
     handle_errors,
     make_headers,
+    normalize_base_url,
     parse_rate_limit,
     parse_response,
     retry_delay,
@@ -97,7 +98,7 @@ def __init__(
 
         self._api_key = api_key
         self._auth_method: AuthMethod = auth_method
-        self._base_url = base_url.rstrip("/")
+        self._base_url = normalize_base_url(base_url)
         self._timeout = timeout
         self._http = httpx.Client(
             base_url=f"{self._base_url}/api/v1",
diff --git a/tests/test_base_url.py b/tests/test_base_url.py
new file mode 100644
index 0000000..47ba3ec
--- /dev/null
+++ b/tests/test_base_url.py
@@ -0,0 +1,23 @@
+from sharpapi import AsyncSharpAPI, SharpAPI
+
+
+def test_sync_client_accepts_api_v1_base_url_without_double_prefix():
+    client = SharpAPI("sk_test", base_url="https://api.sharpapi.io/api/v1/")
+
+    assert str(client._http.base_url) == "https://api.sharpapi.io/api/v1/"
+    assert client._base_url == "https://api.sharpapi.io"
+
+    stream = client.stream.odds()
+    assert stream._url.startswith("https://api.sharpapi.io/api/v1/stream?")
+    assert "/api/v1/api/v1/" not in stream._url
+
+    client.close()
+
+
+async def test_async_client_accepts_api_v1_base_url_without_double_prefix():
+    client = AsyncSharpAPI("sk_test", base_url="https://api.sharpapi.io/api/v1/")
+
+    assert str(client._http.base_url) == "https://api.sharpapi.io/api/v1/"
+    assert client._base_url == "https://api.sharpapi.io"
+
+    await client.close()