In Roman mythology, Vertumnus (Vortumnus, Vertimnus) was the god of seasons, change and plant growth, as well as gardens and fruit trees. He could change his form at will; using this power, he tricked Pomona into marrying him by disguising himself as an old woman.

Vertumnus' cult arrived at Rome around 300 BC (from his Etruscan counterpart: Voltumna) and a temple to him was constructed on the Aventine Hill in 264 BC. A statue of him was placed at the Vicus Tuscus. His festival was the Vertumnalias on August 13.

His name comes from vertere meaning "changing".