diff --git a/langchain/document_loaders/web_base.py b/langchain/document_loaders/web_base.py
index f39f361f..4c7c6cc0 100644
--- a/langchain/document_loaders/web_base.py
+++ b/langchain/document_loaders/web_base.py
@@ -68,17 +68,19 @@ class WebBaseLoader(BaseLoader):
                 "bs4 package not found, please install it with " "`pip install bs4`"
             )
 
-        try:
-            from fake_useragent import UserAgent
-
-            headers = header_template or default_header_template
-            headers["User-Agent"] = UserAgent().random
-            self.session.headers = dict(headers)
-        except ImportError:
-            logger.info(
-                "fake_useragent not found, using default user agent. "
-                "To get a realistic header for requests, `pip install fake_useragent`."
-            )
+        headers = header_template or default_header_template
+        if not headers.get("User-Agent"):
+            try:
+                from fake_useragent import UserAgent
+
+                headers["User-Agent"] = UserAgent().random
+            except ImportError:
+                logger.info(
+                    "fake_useragent not found, using default user agent."
+                    "To get a realistic header for requests, "
+                    "`pip install fake_useragent`."
+                )
+        self.session.headers = dict(headers)
 
     @property
     def web_path(self) -> str:
diff --git a/tests/unit_tests/document_loader/test_web_base.py b/tests/unit_tests/document_loader/test_web_base.py
new file mode 100644
index 00000000..fe6839a5
--- /dev/null
+++ b/tests/unit_tests/document_loader/test_web_base.py
@@ -0,0 +1,10 @@
+from langchain.document_loaders.web_base import WebBaseLoader
+
+
+class TestWebBaseLoader:
+    def test_respect_user_specified_user_agent(self) -> None:
+        user_specified_user_agent = "user_specified_user_agent"
+        header_template = {"User-Agent": user_specified_user_agent}
+        url = "https://www.example.com"
+        loader = WebBaseLoader(url, header_template=header_template)
+        assert loader.session.headers["User-Agent"] == user_specified_user_agent