Mustansiriya Madrasah (Arabic,المدرسة المستنصرية) is a historical building in Baghdad, Iraq. It was the premises of one of the oldest Islamic universities in the world, established in 1227 as a Madrasah by the Abbasid Caliph al-Mustansir making it one of the oldest universities in the world. It is located on the left bank of the Tigris River, the building survived the Mongol invasion of 1258, and has been restored. Nearby buildings included the Saray souq, the Baghdadi Museum, Mutanabbi Street, the Abbasid Palace and Caliph's Street.
In 1235, an early monumental water-powered alarm clock that announced the appointed hours of prayer and the time both by day and by night was completed in the entrance hall of the Mustansiriya Madrasah in Baghdad.