The gens Otacilia, originally Octacilia, was a plebeian family at ancient Rome.
The gens first rose to prominence during the First Punic War, but afterwards lapsed into obscurity.
The first of the family to obtain the consulship was Manius Otacilius Crassus, in 263 BC.
The earliest known member of the family was a native of Maleventum, an ancient city of Campania, which according to Pliny was inhabited by the Hirpini.
The earliest known Otacilius bore the praenomen Numerius, which passed through his daughter to the Fabii.