Walter J. Wolf (also known as Walter Wolf) is one of the villains in Animaniacs. He is the main antagonist of the "Slappy Squirrel" segments. He is Slappy Squirrel's arch-nemesis.

He is constantly trying to defeat Slappy Squirrel, but his plans later fail.

He sometimes teams up with other villains such as Sid the Squid and Beanie the Bison.

In his first appearance, he is voiced by Frank Welker. But, in the rest of his appearances, he was voiced by Jess Harnell, who also voiced Wakko Warner in Animaniacs. Walter has a Yiddish accent as both Harnell and Welker gave him a Yiddish accent.

In the comics, it was revealed that Walter was the star of a TV show that only had 8 episodes and Slappy Squirrel was his sidekick in the show.

Walter had a female look once and it is unknown how he looked like a female.

He also had a non-speaking appearance along with Sid the Squid and Beanie the Bison in the last episode of Animaniacs. This was also the last time that Walter, Sid and Beanie appeared in Animaniacs, making them one of the few characters to not appear in the Animaniacs movie, Wakko's Wish.

He also had a grandson named Stephen Wolf.

Walter is also young when he appeared in Slappy Goes Walnuts, but he did not speak in that episode.

Walter has exploded multiple times, but he survives from the explosions.