In baseball, a wild pitch (abbreviated WP) is charged against a pitcher when his pitch is too high, too short, or too wide of home plate for the catcher to control with ordinary effort, thereby allowing a baserunner, perhaps even the batter-runner on strike three or ball four, to advance.
A wild pitch usually passes the catcher behind home plate, often allowing runners on base an easy chance to advance while the catcher chases the ball down. Sometimes the catcher may block a pitch, and the ball may be nearby, but have trouble finding the ball, allowing runners to advance.
A closely related statistic is the passed ball. As with many baseball statistics, whether a pitch that gets away from a catcher is counted as a wild pitch or a passed ball is at the discretion of the official scorer. The benefit of the doubt is usually given to the catcher if there is uncertainty; therefore, most of these situations are scored as wild pitches. If the pitch was so low as to touch the ground, or so high that the catcher has to jump to get to it, or so wide that the catcher has to lunge for it, it is usually then considered a wild pitch and not a passed ball.
A wild pitch may only be scored if one or more runners advance. If the bases are empty, or the catcher retrieves the ball quickly and the runner(s) are unable to advance, a wild pitch is not charged. A runner who advances on a wild pitch is not credited with a stolen base unless he breaks before the pitcher begins his delivery.
Nolan Ryan is the modern-era leader in the category, throwing 277 wild pitches over his 27 years in Major League Baseball. He also led his league in the category in six different seasons. However, the all-time record belongs to Tony Mullane, who threw 343 in the early years of the game from 1881 to 1894. After Ryan's 277, the next pitcher on the list is Mickey Welch 274, followed by Tim Keefe's 233.
Bill Stemmyer still holds the single-season record, throwing 63 wild pitches in 1886. Since 1900, however, the highest total in a season has been 30 (by Red Ames in 1905). The modern record in a single game is 6, held by three different pitchers.