Class S may refer to:

Class S (culture), early 20th century Japanese social practice of female romantic friendships, and a literary genre depicting this practice Class S, a stellar classification for carbon stars Baltimore and Ohio class S, American steam locomotives BNCR Class S, Irish steam locomotive GNRI Class S, Irish steam locomotive South African Class S 0-8-0, steam locomotives

See also

Type S (disambiguation) S class (disambiguation) S-Type (disambiguation)