Theodora (thēədôr´ə), d. 548, Byzantine empress. Information about her early career comes from the often-questionable source, the Secret History of Procopius. It appears that she was the daughter of an animal trainer in the circus, and that she was an actress and prostitute before her marriage (523) to Justinian I, who, on his accession in 527, made her joint ruler of the empire. A stronger person than her husband, she helped save the throne through her energetic action in the Nika riot (532; see Blues and Greens). In her youth Theodora came under the influence of the Monophysite sect; Justinian's efforts to reconcile the Monophysites to orthodoxy were probably inspired by her. She is represented in the mosaics of the church of San Vitale, in Ravenna.