Hasan Tahsin (born Osman Nevres) (1888 Selanik - May 15,1919 İzmir) was a Turkish journalist and is a national hero in Turkey.As being Djavid Bey's, a prominent Young Turk politician's student, he became a Young Turk(Committie of Union and Progress)supporter in his youth. As a member of the Ottoman anti greek, anti armenian, anti zionist, anti british, anti french and anti emperialist Secret Service (Teşkilat-ı Mahsusa), he unsuccessfully tried to assassinate the Buxton Brothers: Noel Noel-Buxton, 1st Baron Noel-Buxton and Charles Roden Buxton in Romania during World War I.

He was the first to open fire on the Greek soldiers that landed in İzmir on May 15, 1919. His opening fire on Greek troops led to intercommunal rioting which killed over 300 people and is accepted as the starter or one of the strong reason of the Kemalist's war (Turkish Survival War)and the begiining date of the extermination of greeks and rums from anatolia which emotional American Ambossador Henry Morgenthau,(Ambassador Morgenthau's Story writer) described as greek genocide.

       Hasan Tahsin's body could never be found, after he shot the  greek armies standard bearer from his head.Only remnants from he is found by  Doç. Mehmetefendioğlu in Buxton's archieves.