Ohio's 21st senatorial district

Ohio's 21st senatorial district has historically been based in urban Cleveland, Ohio, and consists primarily of Cleveland's West Side neighborhoods of Ohio City and Tremont; Downtown Cleveland; all of Cleveland's East Side neighborhoods; and the cities of Bratenahl, Cleveland Heights, and Shaker Heights. It encompasses Ohio House districts 9, 10 and 11. It has a Cook PVI of D+33.

Its current Ohio Senator is Democrat Dale Martin of Cleveland. Martin was appointed on June 7, 2022, by a caucus of State Senate Democrats after the incumbent senator, Sandra Williams, resigned on June 1.