What is the name of the stepmother's cat?

The stepmother’s cat in Disney’s 1950 Cinderella is named Lucifer.

Lucifer belongs to Lady Tremaine and serves as one of the film’s principal comic antagonists. He repeatedly stalks and torments Cinderella’s mice friends, especially Jaq and Gus, creating a parallel cat-and-mouse storyline alongside Cinderella’s mistreatment by her stepfamily.

The name is sometimes confused with Tom because the sequences echo the visual tradition of theatrical cat-and-mouse cartoons. Lucifer, however, is a distinct Disney character: he is a large, dark-colored cat voiced by June Foray, while the mice and dog Bruno help Cinderella resist him.

Lucifer’s final defeat comes when Bruno chases him away from the house, allowing Cinderella to escape after her stepmother has locked her in the attic. The cat’s role is comic rather than supernatural, despite his infernal-sounding name.