Blackball, black-ball or black ball may refer to:
Society and culture
- Blackballing, ostracizing someone socially, e.g. prevention of finding local or field-specific employment, blacklisting from a club or other organization, etc.
- Blackball, New Zealand, a small town located on the western coast of the South Island of New Zealand; see also Blackball Branch in the "Transportation" section, below.
Games and sporting
- Blackball (pool), a variant of pocket billiards, sanctioned by the World Pool-Billiard Association, popular in the UK and Australia among a few other places, and closely related to the American-style game of eight-ball
- The black ball or 8 ball in that game and in British pool in general
- Blackball, a pejorative term used to represent the Black baseball movement including the formation of Negro league baseball
- Blackball, a monster in the Mystara campaign setting of Advanced Dungeons & Dragons
- "Blackball", a nickname for the letter i flag among the international maritime signal flags, featuring a black solid circle on a yellow background, and having specific additional meanings in certain contexts ("no surfing allowed in this area" at lifeguarded beaches, "no diving allowed in this area" at swimming pools, "gale warning" in a harbor, etc.)
- Black Ball Line (disambiguation), several shipping companies
- Blackball Branch a branch railway line to Blackball, New Zealand (see "Geography" above).
- Black Ball Line, a name for the Puget Sound Navigation Company's ferry system (British Columbia, Canada, and Washington state, US)
- Black Ball Line (trans-Atlantic packet), a fleet of packet ships running between Liverpool and New York, the first scheduled trans-Atlantic service, founded in 1817
- BlackBall, Inc., a producer of digital asset management software.