Theodora (; 980 – late August/early September 1056) was a Byzantine Empress born into the Macedonian dynasty that had ruled the Byzantine Empire for almost two hundred years. She was co-empress with her sister Zoe for two months in 1042 and sole empress regnant from 11 January 1055 to 31 August 1056. She was the last of the Macedonian line, and upon her death the empire entered a period of decline that lasted until the ascension of Alexios I Komnenos in 1081.