Two fluff balls with bites bigger than their barks have been labelled "little heroes" after rescuing their owner from a would-be rapist lurking in a Melbourne cemetery.

RuPaul and Louie "viciously" attacked the unknown man as he held their owner to the ground and tried to pull her pants down at the Williamstown Cemetery.

Victim Kate, not real name, with her little heroes Louie and RuPaul at the Williamstown Cemetery Credit:Eddie Jim

Kate, who asked that her real name not be used, walks the shih tzu and terrier-cross through the cemetery most afternoons but was delayed on Saturday, June 29 until well after dark.

The man attacked from behind at about 8.30pm as Kate waited for the dogs to come back from chasing a rabbit.