Class S

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