A spitball is a baseball pitch in which the ball has been altered by the application of spit, petroleum jelly, or some other foreign substance, such as peanut butter.

Such a pitch presents an additional challenge to the hitter because it causes the ball to move atypically during its approach due to the altered resistance on one side of the ball.

Alternative names for the spitball are mud ball, shine ball and emery ball, although technically, an emery ball is one where the ball has been abraded in much the same way that the original cut ball had been physically cut.

The invention of the spitball is widely credited to Newport, Rhode Island native Frank Corridon, who played for the Chicago Cubs, Philadelphia Phillies, and St. Louis Cardinals.

The spitball was permitted in the major leagues until 1920. Ray Chapman, a shortstop for the American League Cleveland team, was struck by a spitball pitch August 16, 1920 in a game against the New York Yankees following a pitch from Carl Mays. The sound of the ball crashing into Chapman's skull was so loud that Mays thought it hit his bat, fielded the ball, and threw to first base. Chapman died twelve hours later in a New York City hospital. As of 2006, he is the only Major League Baseball player to have been killed in a game. His death helped to outlaw the spitball.

When the prohibition was introduced, it was recognized that there were some professional pitchers who had built their careers in large part on the spitball. A special exception was made for these 17 named players, and they were permitted to throw spitballs for the rest of their careers. Burleigh Grimes lasted the longest of the seventeen, retiring in 1934. The complete list: Doc Ayers (played through 1921); Ray Caldwell (1921); Stan Coveleski (1928); Bill Doak (1929); Phil Douglas (1922); Red Faber (1933); Dana Fillingim (1925); Ray Fisher (1920); Marv Goodwin (1934); Burleigh Grimes (1934); Dutch Leonard (1925); Clarence Mitchell (1932); Jack Quinn (1933); Allen Russell (1925); Dick Rudolph (1927); Urban Shocker (1928); and Alan Sothoron (1926).

Although the spitball is now banned at all levels of professional and organized amateur baseball, it is still sometimes thrown in violation of the rules. Typically, a lubricant is hidden behind the pitcher's knee or under the peak of his cap. Others will place the ball in their mitt and then cough or lick onto it. Another tactic pitchers use is to soak their hair in water before going out to the mound, and then rubbing their hand in their hair before a pitch. Some pitchers have even glued a piece of sandpaper to one of their fingers, and scuffed a part of the ball to achieve a similar effect to the spitball. Ted "Double Duty" Radcliffe has stated that he would hide a piece of emery board in his belt buckle so that he could roughen the ball or even cut it. During the Minnesota Twins' 1987 pennant chase, one of their starting pitchers, Joe Niekro, was suspended when he was caught on the field with a nail file in his back pocket. Niekro's defense that he had been filing his nails in the dugout was ignored.

One of the most famous spitballers was Preacher Roe, who played for the Brooklyn Dodgers in the 1950s. Roe was renowned for his ability to control the spitball, and for his ability to throw it illegally without getting caught. Another famous user of the pitch was Gaylord Perry, who went so far as to title his autobiography Me and the Spitter. (For example, Gaylord would sniff red peppers to make his nose run or he'd put vaseline on his zipper because umps would never check there.)

The name dry spitter is sometimes used to describe a pitch that moves like a spitball without saliva, such as the forkball or split-finger fastball. It is sometimes used simply as slang for the knuckleball.

Baseball pitches