The 31 March incident was a political crisis within the Ottoman Empire in April 1909, during the Second Constitutional Era. The incident broke out during the night of 30–31 Mart 1325 in Rumi calendar, thus named after 31 March where March is the equivalent to Rumi month Mart. Occurring soon after the 1908 Young Turk Revolution, in which the Committee of Union and Progress (CUP) had successfully restored the Constitution and ended the absolute rule of Sultan Abdul Hamid II, it is sometimes referred to as an attempted countercoup or counterrevolution. It consisted of a general uprising against the CUP within Istanbul, largely led by reactionary groups, particularly Islamists opposed to the secularising influence of the CUP and supporters of absolutism, although liberal opponents of the CUP within the Liberty Party also played a lesser role. The crisis ended after eleven days, when troops loyal to the CUP restored order in Istanbul and deposed Abdul Hamid.

Hüseyin Hilmi Pasha was an Ottoman statesman and imperial administrator. He was twice the Grand Vizier of the Ottoman Empire around the time of the Second Constitutional Era. He was also one-time president of the Turkish Red Crescent.