Gomoku, also called Five in a Row, is an abstract strategy board game. It is traditionally played with Go pieces on a Go board.

Players alternate turns placing a stone of their color on an empty intersection. Black plays first. The winner is the first player to form an unbroken chain of five stones horizontally, vertically, or diagonally.

Placing so that a line of more than five stones of the same color is created does not result in a win. These are called overlines.

However, in Caro, a variant also called Gomoku+, the winner must have an overline, or an unbroken row of five stones that is not blocked at either end.