Ondokuz Mayıs University (Turkish: Ondokuz Mayıs Üniversitesi, abbreviated OMÜ) is a public research university located in Samsun, a city on Turkey's Black Sea coast. It was established on 1 April 1975 and takes its name from 19 May, the date in 1919 when Mustafa Kemal Atatürk arrived in Samsun to begin the Turkish War of Independence. The university grew out of the Samsun Faculty of Medicine, which had been founded two years earlier in 1973, and it has since developed into one of the larger state institutions in the region.

The university's principal campus sits in the Atakum district on the outskirts of Samsun, overlooking the Black Sea and the slopes of Kocadağ. Academically, OMÜ is organised into sixteen faculties, a state conservatoire, three schools, eleven vocational schools and five institutes. Its faculties cover a broad range of disciplines, among them medicine, dentistry, engineering, agriculture, education, law and veterinary medicine. The Faculty of Medicine operates a large teaching hospital that provides healthcare across the surrounding Black Sea provinces. Over the years several units originally attached to the university were reorganised into separate institutions, contributing to the creation of Amasya, Ordu and Sinop universities.

During the 2013-2014 academic year the university recorded roughly 28,400 undergraduate, 4,700 graduate and 10,900 associate-degree students, for a total of about 43,900. OMÜ maintains an international profile through numerous Erasmus and Mevlana exchange agreements and cooperation protocols with partner institutions abroad, hosting around 1,750 international students from some 80 countries. It is a member of the European University Association. In EduRank's 2026 assessment the university placed 26th nationally among Turkish institutions and 1,562nd worldwide.