Black Flag can refer to:

• Black Flag is a punk rock band.
• Black Flag is the name of an anarchist newspaper.
• Black Flag is a brand of insecticide made by the Clorox company.
• The Black Flag is a progressive website based in Roswell, NM (www.theblackflag.org).
• Black Flags was a bandit unit operating around Hanoi in the late 19th century

Additionally, "black flag" may refer to an actual flag:

• The Anarchist black flag has been an anarchist symbol since the 1880s. Anarchists use either a plain black flag or a black flag with an "A" for anarchy inside a circle for unity.
• Black flags are often associated with funerals, particularly state funerals and public mourning.
• A black flag was the first and only symbol used by Muhammad to represent his new religion,
• Islamic terrorism organization Al Qaeda has been known to fly a black flag in its training camps. Their use of the flag is related to the original use by Muhammad..
• Black Flag is another name for the Jolly Roger, a skull and crossbones on a black background, and is associated with pirates.
• In auto racing, a black flag is used to signal a driver to come into the pits.
• In the game Dance Dance Revolution a black flag is a score of all 'perfect' except for one 'great', just missing out on the coveted AAA grade.