Captain Boomerang is the name of two supervillains appearing in American comic books published by DC Comics, who respectively serve as enemies to both the Barry Allen and Wally West versions of the Flash. Created by writer John Broome and artist Carmine Infantino, the first Captain Boomerang, George "Digger" Harkness, first appeared in The Flash #117 (December 1960). He has also been a prominent member of the Suicide Squad since its second iteration in the late 1980s. During the 2004 storyline Identity Crisis, George Harkness is killed and his son, Owen Mercer, created by Brad Meltzer and Michael Turner, takes over his father's role as Captain Boomerang for a period of time. However, during the 2009–2010 Blackest Night storyline, Owen is killed and Harkness returns to life, resuming his role as Captain Boomerang, and, overwhelmed by grief and rage, evolves as a dangerous threat after the loss of his son.
Both Harkness and Mercer have been adapted from the comics into various forms of media, including television series, feature films, and video games. In particular, Harkness appeared in the Arrowverse television series Arrow, portrayed by Nick E. Tarabay, and the DC Extended Universe films Suicide Squad (2016) and The Suicide Squad (2021), portrayed by Jai Courtney. Additionally, Mercer appears in the Arrowverse series The Flash, portrayed by Richard Harmon.