Gaius Trebatius Testa (fl. 1st century BC) was a jurist of ancient Rome, whose family, and himself, originated from Elea.

He was a protégé of Cicero; Cicero dedicated his Topica to Trebatius, and recommended Trebatius as a legal advisor to Julius Caesar. Trebatius enjoyed Caesar's favor, and later that of Augustus as well.

Trebatius' writings included a de religionibus and de iure civili, but not even excerpts of these survive. He was, however, frequently cited by later jurists, and also had a high reputation as the teacher of Marcus Antistius Labeo.