In chess the fianchetto (Italian "little flanking") is a pattern of development wherein a bishop is developed to the second rank of the adjacent knight file, the knight pawn having been moved one or two squares forward. In Italian, fianchetto is pronounced with a hard k sound as in "cat", but many English-speaking chess players mispronounce this word with a ch sound as in "church".

The fianchetto is a staple of many "hypermodern" openings, whose philosophy is to relinquish pawn control of the center in the hope of later undermining the opponent's overextended pawn structure. It also regularly occurs in the so-called "Indian" defences, since fianchettoing was the standard practice in chess as it was played in ancient India, presumably because the bishop was of limited mobility.

Common openings with a fianchetto include the Sicilian (dragon variation), Modern (Pirc defence), and Benoni systems