Nicholas Mysticus (d. May 925) was the Patriarch of Constantinople from 893 to 906 and from 912 to 925. He denied a fourth marriage to emperor Leo VI, and unsuccessfully plotted against Leo to place Andronicus Ducas on the throne. Nicholas was forced to baptize Leo's illegitimate son, and was then deposed in 906. He was restored to power when Leo's brother Alexander III became emperor, and became regent for Constantine VII when Alexander quickly died. As regent he had his co-regent Constantine Ducas executed, and made an unpopular peace with the Bulgars. He was replaced as regent by Romanus I, but was allowed to remain patriarch until his death in 925.
