International Socialism (ISJ) is a quarterly journal of socialist theory published by the British Socialist Workers Party and currently edited by Chris Harman.

The current journal is the second series following an earlier series which ran from 1960 to 1977 publishing a total of 104 issues. However, a single issue of a duplicated journal of this name had been published in 1958 and the first edition of Tony Cliff's essay on Rosa Luxemburg was published, in book form, as issue 2/3 in series with this otherwise one off publication.
Christopher Hitchens is among the journal's alumni.