Acilius (fem. Acilia) was the nomen of the gens Acilia, a patrician family of ancient Rome. Branches of the family included the Acilii Balbi and the Acilii Glabriones; a tomb of the latter was found in Rome in 1888. The Glabriones also had a garden, the Horti Aciliorum, on the Pincian Hill in the 2nd century.

• Acilius Glabrio
• Caius Acilius
• Manius Acilius Aviola
• Manius Acilius Balbus
• Manius Acilius Faustinus
• Manius Acilius Glabrio
• Manius Acilius Rufus
• Manius Acilius Severus

In biology, Acilius is a genus of water beetle (Dytiscidae).