Conan II of Rennes (c. 1033 – 11 December 1066) is Duke of Brittany from 1040 to his death.

Conan is the eldest child and heir of Alan III, Duke of Brittany by his wife Bertha of Blois, and member of the House of Rennes.

He is the elder brother of Hawise, who succeeds him as suo jure duchess.