A puck is a vulcanized, hard rubber disk used in ice hockey, one inch thick (25.4 mm) and 3 inches in diameter (76.2 mm), and weighing between 5.5 to 6 oz (156-170 g). It is frozen a few hours before the game to prevent bouncing. Pucks can reach speed of 100 mph (160 km/h) when hit by players' sticks, and spectators at hockey games are occasionally injured. On March 18, 2002, a thirteen year old girl, Brittany Cecil, was killed by a hockey puck at a Columbus Blue Jackets game.

The origin of the word is obscure, but evidently not connected to Shakespeare's Puck or the mythical Puck. The Oxford English Dictionary suggests the name is related to the verb to puck (a cognate of poke) used in hurling for striking or pushing the ball.

The phrase "dumb as a hockey puck" was once somewhat common; in an ironic twist the smart puck was developed in the late 1990s, which had integrated electronics to track its position, letting TV stations highlight it on the screen.

Ice hockey evolved from field hockey played on ice surfaces in Canada. The early players found that the rubber ball used in field hockey was far too active on the hard ice surface, so they cut off the top and bottom of the ball to form the hockey puck.