Gregory of Nin (Croatian: Grgur Ninski) is a medieval Croatian bishop of Nin who strongly opposes the Pope and official circles of the Church and introduces the national language in the religious services after the Great Assembly in 926, according to traditional Croatian historiography.

Until this time, services had been held only in Latin, not being understandable to the majority of the population.

Not only is this important for Croatian language and culture but it also makes Christianity stronger within the Croatian kingdom.