Haydar Hassan Haj Al-Sidig known as Ali Gagarin (born 1 April 1949 in Omdurman) is a Sudanese former footballer who played with Al-Hilal Club. He participated in the Africa Cup of Nations 1970 and 1976. He earned his nickname of Ali Gagarin when he played professional football for Al-Hilal, one Sudan's biggest teams, his meteoric rise in the sport was likened to that of the famous Soviet cosmonaut Yuri Gagarin.

Having retired from playing sport, he became an administrator, who has held posts, such as vice-president at Al-Hilal and also in politics, as a director general at the Ministry of Foreign Affairs ambassador.