What is the name of Data's pet cat?

Data’s pet cat is named Spot.

Spot is the android Data’s companion aboard the USS Enterprise-D in Star Trek: The Next Generation. The cat is introduced in “Data’s Day,” the fourth-season episode that follows Data as he observes the human rituals and anxieties surrounding Miles O’Brien and Keiko Ishikawa’s wedding.

Spot is a memorable contrast to Data’s logical, mechanical nature. Data studies cat care and behavior with characteristic seriousness, while Spot remains an ordinary, independent animal. The cat appears in several later TNG episodes and in Star Trek films, including Star Trek Generations and Star Trek: Nemesis.

One unusual continuity detail is that Spot’s presentation changes. The cat first appears as a male Somali cat, then later appears as a female orange tabby and gives birth to kittens in “Genesis.” Those changes do not alter the canonical name. Whiskers, Lucky, and Chester are not Data’s established pet in the series.