Alexander (Greek: Αλέξανδρος), sometimes numbered Alexander III, ruled as Emperor of the Byzantine Empire in 912–913.
Alexander was the third son of Emperor Basil I and Eudokia Ingerina. Unlike his older brother Leo VI the Wise, his paternity was not disputed between Basil I and Michael III because he was born years after the death of Michael. As a child, Alexander was crowned as co-emperor by his father around 879.
Upon the death of his brother Leo on 11 May 912, Alexander succeeded as senior emperor alongside Leo's young son Constantine VII. He was the first Byzantine emperor to use the term "autocrator" (αὐτοκράτωρ πιστὸς εὑσεβὴς βασιλεὺς) on coinage to celebrate the ending of his thirty-three years as co-emperor.