In the sport of cricket, a bouncer (or bumper) is a type of delivery, usually bowled by a fast bowler. It is pitched short so that it bounces on the pitch well short of the batsman and rears up to chest or head height (or even higher) as it reaches the batsman.
Bouncers are used tactically to drive the batsman back on to his back foot if he has been freely playing front foot scoring shots, such as drives. To this end, bouncers are usually directed more or less at the line of the batsman's body. Aiming at the batsman is not illegal provided the ball bounces on the pitch or is below the waist height, and is a tactically important part of the game. Aiming at the batsman's head without bouncing on the pitch, known as a beamer, is illegal.
A batsman may play a bouncer in either a defensive or an attacking way. If the batsman plays it defensively he aims primarily to avoid getting out, and secondarily to avoid being hit by the ball. For a head-high bouncer, these goals are achieved most easily by ducking under the ball. If the ball is at chest height, the batsman's best defence is to move on to his back foot, raise his bat vertically to chest height, and attempt to block the ball and direct it downwards to the pitch so as to avoid presenting a catch to a fielder. Sometimes the batsman will need to jump into the air to gain the necessary height to defend with the bat. He may also sway out of the way. Given these approaches, the bowler can hope to both intimidate the batsman somewhat, and possibly have the ball deflect off the bat at an awkward angle and produce a catch for a nearby fielder.
Conversely, the bouncer can be a very productive ball for the batsman, if he plays it in an attacking manner. The shot that is used to attack the bouncer is the hook shot. To play the hook shot the batsman moves his back foot backwards and towards the off side as the ball is being delivered. As the ball approaches, the batsman swivels from facing the off side to facing the leg side, while holding the bat horizontally. The batsman's aim is to hit the ball at high speed towards, into or over the leg side boundary. However, despite their run-scoring potential, hook shots frequently lead to wickets falling, particularly through balls hitting the top edge of the bat and being caught by leg side fielders. However, if the bouncer is misdirected by the bowler, and reaches the batsman on the off side of his wicket, the cut, uppercut or late cut can be played, either with the intention of guiding the ball along the ground, through a gap in the field setting, or over the infield for four or six.
There is an unspoken agreement, particularly in the time before the widespread use of batting helmets, that fast bowlers will not bowl bouncers at each other, because less skilled batsmen are less likely to effectively defend and therefore more likely to be struck. Breaking of this rule can lead to 'bouncer wars'.
Because of the potential danger to batsmen of being hit and to stop bowlers bowling bouncers all the time, there are laws in the Laws of Cricket governing how frequently a bowler may bowl bouncers, as well as how many fielders may field backward of square leg. These laws take into account the relative skill of the batsmen.
During the 1970s to 1980s, bouncers were used as part of a team's intimidatory tactics, especially by the West Indies team. In 1991, the International Cricket Council introduced a "one bouncer per batsman per over" rule in an attempt to discourage use of intimidation. However, the ruling was not well received by players and umpires alike, with English umpire Dickie Bird describing it as "farcical" as he felt that calling intimidatory tactics should be left to the umpire. The ICC changed it to two bouncers per over in 1994, with a two-run no-ball penalty (rather than one-run no-ball) if the bowler exceeded two bouncers an over. ICC reverted again to one bouncer per over in 2001 (and a one-run no-ball in case a bowler exceeded the limit).
On October 29, 2012 The International Cricket Council increased the number of bouncers that could be bowled during a One Day International to two. The number of bouncers per over allowed in T20s was kept to one.
Fast leg theory, the deliberate and sustained bowling of bouncers aimed at the body, was a tactic used by England against Australia in 1932/33, dubbed the Bodyline series by the Australians. This controversial tactic caused the Laws of Cricket to be reformed to prevent any recurrence.
In 1954-55 at Sydney the England fast bowler Frank Tyson bowled bouncers at the Australian Ray Lindwall, who returned the favour by hospitalising Tyson with one of his own. An angry Tyson returned with a large lump on his head and took 6/85 in the second innings to give England a 38-run victory. More recently in 1994 at the Oval Devon Malcolm was hit on the helmet by a bouncer from Fanie de Villiers. The incensed Malcolm told the South Africans "You guys are history" and took apart their second innings with 9/57.
There have been several occurrences of injurious bouncers in recent times. In 2006, Australian opener Justin Langer, was struck on the head in his 100th Test from a bouncer from Makhaya Ntini and hospitalised. In 2008 West Indies batsman Shivnarine Chanderpaul was knocked out for several minutes after being hit by a bouncer from Australian fast bowler Brett Lee during a test match. Shoaib Akhtar was a regular offender; he injured both Gary Kirsten (2003) and Brian Lara (2004) with fast bouncers. Both batsmen had to be taken off the field. 
- "Bird wants end to bouncer rule". independent.co.uk. 28 February 1994.
- ICC Changes rules on the bouncer again
- "Cricket's Turning Points: The bouncer rule". Cricinfo.
- "ICC paves way for Day-Night Tests". Wisden India. 29 October 2012.
- "Brett Lee bumper KO's runmaker Chanderpaul". The Courier-Mail. 26 May 2008.
- Shoaib injured Lara and Kirsten