@@ -70,6 +70,11 @@ class ClientOptions(object):
         scopes (Optional[Sequence[str]]): OAuth access token override scopes.
         api_key (Optional[str]): Google API key. ``credentials_file`` and
             ``api_key`` are mutually exclusive.
+        api_audience (Optional[str]): The intended audience for the API calls
+            to the service that will be set when using certain 3rd party
+            authentication flows. Audience is typically a resource identifier.
+            If not set, the service endpoint value will be used as a default.
+            An example of a valid ``api_audience`` is: "https://language.googleapis.com".
 
     Raises:
         ValueError: If both ``client_cert_source`` and ``client_encrypted_cert_source``
@@ -85,6 +90,7 @@ def __init__(
         credentials_file=None,
         scopes=None,
         api_key=None,
+        api_audience=None,
     ):
         if client_cert_source and client_encrypted_cert_source:
             raise ValueError(
@@ -99,6 +105,7 @@ def __init__(
         self.credentials_file = credentials_file
         self.scopes = scopes
         self.api_key = api_key
+        self.api_audience = api_audience
 
     def __repr__(self):
         return "ClientOptions: " + repr(self.__dict__)
 
@@ -36,6 +36,7 @@ def test_constructor():
             "https://www.googleapis.com/auth/cloud-platform",
             "https://www.googleapis.com/auth/cloud-platform.read-only",
         ],
+        api_audience="foo2.googleapis.com",
     )
 
     assert options.api_endpoint == "foo.googleapis.com"
@@ -46,6 +47,7 @@ def test_constructor():
         "https://www.googleapis.com/auth/cloud-platform",
         "https://www.googleapis.com/auth/cloud-platform.read-only",
     ]
+    assert options.api_audience == "foo2.googleapis.com"
 
 
 def test_constructor_with_encrypted_cert_source():
@@ -114,6 +116,7 @@ def test_from_dict():
                 "https://www.googleapis.com/auth/cloud-platform",
                 "https://www.googleapis.com/auth/cloud-platform.read-only",
             ],
+            "api_audience": "foo2.googleapis.com",
         }
     )
 
@@ -126,6 +129,7 @@ def test_from_dict():
         "https://www.googleapis.com/auth/cloud-platform.read-only",
     ]
     assert options.api_key is None
+    assert options.api_audience == "foo2.googleapis.com"
 
 
 def test_from_dict_bad_argument():
Original file line number	Diff line number	Diff line change
`@@ -36,6 +36,7 @@ def test_constructor():`
`36`	`36`	`"https://www.googleapis.com/auth/cloud-platform",`
`37`	`37`	`"https://www.googleapis.com/auth/cloud-platform.read-only",`
`38`	`38`	`],`
	`39`	`+ api_audience="foo2.googleapis.com",`
`39`	`40`	`)`
`40`	`41`
`41`	`42`	`assert options.api_endpoint == "foo.googleapis.com"`
`@@ -46,6 +47,7 @@ def test_constructor():`
`46`	`47`	`"https://www.googleapis.com/auth/cloud-platform",`
`47`	`48`	`"https://www.googleapis.com/auth/cloud-platform.read-only",`
`48`	`49`	`]`
	`50`	`+ assert options.api_audience == "foo2.googleapis.com"`
`49`	`51`
`50`	`52`
`51`	`53`	`def test_constructor_with_encrypted_cert_source():`
`@@ -114,6 +116,7 @@ def test_from_dict():`
`114`	`116`	`"https://www.googleapis.com/auth/cloud-platform",`
`115`	`117`	`"https://www.googleapis.com/auth/cloud-platform.read-only",`
`116`	`118`	`],`
	`119`	`+ "api_audience": "foo2.googleapis.com",`
`117`	`120`	`}`
`118`	`121`	`)`
`119`	`122`
`@@ -126,6 +129,7 @@ def test_from_dict():`
`126`	`129`	`"https://www.googleapis.com/auth/cloud-platform.read-only",`
`127`	`130`	`]`
`128`	`131`	`assert options.api_key is None`
	`132`	`+ assert options.api_audience == "foo2.googleapis.com"`
`129`	`133`
`130`	`134`
`131`	`135`	`def test_from_dict_bad_argument():`