Moving the goalposts is a metaphor, derived from goal-based sports such as football and hockey, that means to change the rule or criterion (goal) of a process or competition while it is still in progress, in such a way that the new goal offers one side an advantage or disadvantage.

In sport, a goal may refer to either an instance of scoring, or to the physical structure or area where an attacking team must send the ball or puck in order to score points. The structure of a goal varies from sport to sport, and one is placed at or near each end of the playing field for each team to defend. For many sports, each goal structure usually consists of two vertical posts, called goal posts, supporting a horizontal crossbar. A goal line marked on the playing surface between the goal posts demarcates the goal area. Thus, the objective is to send the ball or puck between the goal posts, under or over the crossbar, and across the goal line. Other sports may have other types of structures or areas where the ball or puck must pass through, such as the basketball hoop. Sports which feature goal scoring are also commonly known as invasion games.