Culture Bomb is a special effect in Civilization VI which instantly expands a civilization's territory into nearby neutral, or even foreign-owned territory. Culture bombing is the only way of taking non-neutral territory in the game, barring military conquest or diplomatic negotiations involving switching cities.
The Culture Bomb is triggered on a specific tile (usually by building a tile improvement or district). The result is the immediate annexation of the six tiles surrounding the trigger tile, without districts or wonders and falling within 3 hexes of one of the owner's City Centers. Tiles in which wonders or districts are being constructed are still flipped under the effect of a Culture Bomb, wiping out any unfinished construction in the process.
A Culture Bomb may be triggered by a number of special sources within the game. Typically it is the case of civilization-specific abilities, such as Poland's ability Golden Liberty (by building Encampments or Forts), Australia's ability Land Down Under (by building Pastures), the Dutch ability Grote Rivieren (by building Harbors), the Māori ability Mana (by building Fishing Boats), the Gallic ability Hallstatt Culture (by building Mines, although they only claim unowned tiles), and Jayavarman VII's leader ability Monasteries of the King (by building Holy Sites).
Nonspecific Culture Bombs can be unlocked via other means. Notably, the Enhancer Belief Burial Grounds lets any civilization Culture Bomb by building a Holy Site (though in Gathering Storm, this belief is removed and the Culture Bomb ability is associated with the Follower Belief Warrior Monks), and the Great Engineer Mimar Sinan grants it (with Rise and Fall) when building an Industrial Zone. In the Vietnam & Kublai Khan Pack, the Preserve initiates a Culture Bomb upon completion, but only claims adjacent unowned tiles. The World Congress resolution Border Control Treaty will trigger a Culture Bomb upon the completion of any district to whoever wins it.