Add `Unauthenticated` exception.

1 files changed, 11 insertions, 2 deletions

diff --git a/docs/api-guide/exceptions.md b/docs/api-guide/exceptions.md
index c3bdb7b9..f5dff94a 100644
--- a/docs/api-guide/exceptions.md
+++ b/docs/api-guide/exceptions.md
@@ -49,11 +49,19 @@ Raised if the request contains malformed data when accessing `request.DATA` or `
 
 By default this exception results in a response with the HTTP status code "400 Bad Request".
 
+## Unauthenticated
+
+**Signature:** `Unauthenticated(detail=None)`
+
+Raised when an unauthenticated incoming request fails the permission checks.
+
+By default this exception results in a response with the HTTP status code "401 Unauthenticated", but it may also result in a "403 Forbidden" response, depending on the authentication scheme in use.  See the [authentication documentation][authentication] for more details.
+
 ## PermissionDenied
 
 **Signature:** `PermissionDenied(detail=None)`
 
-Raised when an incoming request fails the permission checks.
+Raised when an authenticated incoming request fails the permission checks.
 
 By default this exception results in a response with the HTTP status code "403 Forbidden".
 
@@ -81,4 +89,5 @@ Raised when an incoming request fails the throttling checks.
 
 By default this exception results in a response with the HTTP status code "429 Too Many Requests".
 
-[cite]: http://www.doughellmann.com/articles/how-tos/python-exception-handling/index.html
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+[cite]: http://www.doughellmann.com/articles/how-tos/python-exception-handling/index.html
+[authentication]: authentication.md
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