Theoclia (flourished 3rd century, died 218) was a Syrian Roman noblewoman. Theoclia was most probably born and raised in Arca Caesarea (modern Arqa, Lebanon). She was a daughter of the Roman Equestrian Promagistrate Marcus Julius Gessius Marcianus and his wife, Julia Avita Mamaea. She was a sister of the Roman emperor Alexander Severus, who ruled from 222 until 235. She may have had an elder brother called Marcus Julius Gessius Bassianus who served as a Magister (master) in the Arval Brethren during the reign of Roman emperor Caracalla who ruled from 212 until 217. Through her mother, Theoclia was related to the royal family of Emesa and the Severan dynasty of the Roman Empire. The only two Roman historical sources that mention her are the Roman History by Cassius Dio who mentions Theoclia