SS Demosthenes can refer to:
- SS Demosthenes (1911), a UK ocean liner built in 1911 and scrapped in 1931
- USS William Isom (ID-1555), an oil tanker built in the USA in 1917, renamed Demosthenes and registered in Panama in 1948; she was scrapped in 1955
This article includes a list of ships with the same or similar names. If an internal link for a specific ship led you here, you may wish to change the link to point directly to the intended ship article, if one exists.