The Cat Who Walks Through Walls is a science fiction novel by Robert A. Heinlein published in 1985. It is one of the 'Lazarus Long' set of books.

A writer seated at the best restaurant on the space station is approached by a man who desperately but cryptically urges him to "kill Tolliver" before being shot in front of the writer's eyes. The writer is joined by a beautiful and sophisticated lady who helps him flee with a bonsai and a would-be murdering bum to Luna.

The Cat Who Walks Through Walls may be regarded as part of Heinlein's multiverse series, or as a sequel to both Number of the Beast and The Moon is a Harsh Mistress.