Ummidius is a Roman nomen gentilicium. Notable people with the name include:
Gaius Ummidius Actius Anicetus, Roman pantomime actor Gaius Ummidius Durmius Quadratus (c. 12 BC – c. 60 AD), Roman senator Gaius Ummidius Quadratus, Roman consul Gaius Ummidius Quadratus Sertorius Severus, Roman senator Marcus Ummidius Quadratus Annianus (138–182), Roman Senator