Theotimus of Tomi was a late antique historian from the city of Tomi on the Black Sea coast. He is known solely from a citation by the 5th-century church historian Socrates Scholasticus, which places his life and work in the late 4th or early 5th century CE.

His only attested work is a lost History of the Goths. Socrates records that Theotimus detailed the Goths' conversion to Christianity during the era of the Arian bishop Ulfilas. No further biographical details survive.

Theotimus is significant as a lost source. His work provided an early Roman provincial perspective on the Goths and was used as an authority by Socrates Scholasticus. His location in Tomi, a city directly affected by Gothic settlements, suggests his history contained valuable local testimony on Gothic-Roman relations and the spread of Arian Christianity.