Bill the cat is a fictional cat-based character in the Bloom County cartoon strip. His most frequent spoken sentiments are "Ack!" and "Thbbbt!". These statements were often used in the cartoon as a social indictment of policy or popular opinion in the 1980s United States.

He spent time as an unintelligible rock star who played lead electric tongue with his band Deathtöngue, later Billy and the Boingers. Soon after, Bill joined and became the leader of an enigmatic Hare Krishna-type cult.

Bill the Cat twice won the National Radical Meadow Party's nomination to run for President of the United States, in 1984 and 1988, despite being dead in the first instance (official cause: acne), and despite having a vocabulary that mainly consisted of "Ack!" he lost twice. This did not stop him from selling secrets to communist Russia, embarking on a torrid love affair with Jeane Kirkpatrick and being used as the primary source for an illegal cat-sweat-based baldness cure. He also swapped brains with Donald Trump (who had been hit with a cruise boat anchor while sunbathing in New York harbor).

Bill the Cat was last seen peeking in from one side of the panel in the Opus comic strip. Given his ostensible death and revival by tongue cloning (a la Sleeper), his carcass was suggested as the source of the recent BSE epidemic. However, he has recently been chosen as the new mayor of Bloom County. He got the message when he was playing Garfield at a mall promotion (the child in his lap asked her father if Garfield had died). Recent mayoral efforts for Bill and Opus are forcing low-jeans teenagers to wear suspenders. Bill, however, lost an election a few months later because of an affair with Paris Hilton.

Bill the Cat is commonly seen as a parody of Jim Davis' Garfield, an attempt to create a character so repulsive that it would have absolutely no merchandising potential. Ironically, Bill the Cat trinkets and figurines have sold in great quantity.