I Gymnasium Osijek (Croatian: I. gimnazija Osijek) is a high school in Osijek, Croatia.

The school was established on 1 September 1992, when Assembly of Osijek Municipality reorganized Center for vocational education "Ribar Brothers" (Croatian: Centar za usmjereno obrazovanje "Braća Ribar").

From school year of 1991-92 till 1999-00 in school was realized part of program of general gymnasium for students of Franjo Kuhač Music School.