In basketball, a block (short for blocked shot), not to be confused with blocking, occurs when a defensive player legally deflects a field goal attempt from an offensive player. The defender must not touch the offensive player's hands or otherwise a foul is called. In order to be legal, the block must occur while the shot is traveling upward or at its apex. If it is heading downward when the defender hits it, it is ruled as goaltending and counts as a made basket. Goaltending is also called if the block is made after the ball bounces on the backboard (NFHS excepted; the NCAA also used this rule until the 2009–10 season). Nicknames for blocked shots include "rejections," "stuffs," "facials," "swats," "denials," and "packs." Blocked shots were first officially recorded in the NBA during the 1973-74 season.

Largely due to their height and position near the basket, centers and power forwards tend to record the most blocks, but shorter players with high leaps can also be blockers, an example being Dwyane Wade, the shortest player, at 6'4", to record 100 blocked shots in a single season. A player with the ability to block shots can be a positive asset to a team's defense, as they can make it difficult for opposing players to shoot near the basket and by keeping the basketball in play, as opposed to swatting it out of bounds, a blocked shot can lead to a fast break, a skill Bill Russell was notable for. To be a good shot-blocker, a player needs great court sense and timing, and good height or jumping ability. One tactic is that a shot-blocker can intimidate opponents to alter their shots, resulting in a miss.

Block may refer to:

Basketball is a team sport, the objective being to shoot a ball through a basket horizontally positioned to score points while following a set of rules. Usually, two teams of five players play on a marked rectangular court with a basket at each width end. Basketball is one of the world's most popular and widely viewed sports.

A regulation basketball hoop consists of a rim 18 inches in diameter and 10 feet high mounted to a backboard. A team can score a field goal by shooting the ball through the basket during regular play. A field goal scores two points for the shooting team if a player is touching or closer to the basket than the three-point line, and three points (known commonly as a 3 pointer or three) if the player is behind the three-point line. The team with the most points at the end of the game wins, but additional time (overtime) may be issued when the game ends with a draw. The ball can be advanced on the court by bouncing it while walking or running (dribbling) or throwing (passing) it to a teammate. It is a violation to move without dribbling the ball (traveling), to carry it, or to double dribble (to hold the ball with both hands then resume dribbling).