Checkmate, a division of Task Force X, is a fictional covert operations agency appearing in American comic books published by DC Comics. The antihero team first appeared in Action Comics #598 and proceeded to have its own ongoing title in Checkmate! In the wake of events depicted in the mini-series The OMAC Project and Infinite Crisis, Checkmate is re-chartered as a United Nations Security Council-affiliated agency and was again given its own series, Checkmate.

Action Comics is an American comic book/magazine series that introduced Superman, one of the first major superhero characters. The publisher was originally known as National Allied Publications, and later as National Comics Publications and as National Periodical Publications, before taking on its current name of DC Comics. Its original incarnation ran from 1938 to 2011 and stands as one of the longest-running comic books with consecutively numbered issues. The second volume of Action Comics beginning with issue #1 ran from 2011 to 2016. Action Comics returned to its original numbering beginning with issue #957.