diff --git a/sphinx/writers/html.py b/sphinx/writers/html.py
index 34b73a0a5c3..e0f10862e8a 100644
--- a/sphinx/writers/html.py
+++ b/sphinx/writers/html.py
@@ -612,7 +612,7 @@ def visit_image(self, node: Element) -> None:
         # rewrite the URI if the environment knows about it
         if olduri in self.builder.images:
             node['uri'] = posixpath.join(self.builder.imgpath,
-                                         self.builder.images[olduri])
+                                         urllib.parse.quote(self.builder.images[olduri]))
 
         if 'scale' in node:
             # Try to figure out image height and width.  Docutils does that too,
diff --git a/sphinx/writers/html5.py b/sphinx/writers/html5.py
index b9d0f648c94..d94596955ab 100644
--- a/sphinx/writers/html5.py
+++ b/sphinx/writers/html5.py
@@ -560,7 +560,7 @@ def visit_image(self, node: Element) -> None:
         # rewrite the URI if the environment knows about it
         if olduri in self.builder.images:
             node['uri'] = posixpath.join(self.builder.imgpath,
-                                         self.builder.images[olduri])
+                                         urllib.parse.quote(self.builder.images[olduri]))
 
         if 'scale' in node:
             # Try to figure out image height and width.  Docutils does that too,