George Edward "Rube" Waddell (October 13, 1876 – April 1, 1914) was an American pitcher in Major League Baseball (MLB). A left-hander, he played for 13 years, with the Louisville Colonels, Pittsburgh Pirates, and Chicago Orphans in the National League, as well as the Philadelphia Athletics and St. Louis Browns in the American League. Born in Bradford, Pennsylvania, and raised in Prospect, Pennsylvania, Waddell was elected to the Baseball Hall of Fame in 1946.

Waddell is best remembered for his highly eccentric behavior, and for being a remarkably dominant strikeout pitcher in an era when batters were expert at making contact. He had an excellent fastball, a sharp-breaking curveball, a screwball, and superb control; his strikeout-to-walk ratio was almost 3-to-1, and he led the major leagues in strikeouts for six consecutive years.

Waddell was born on October 13, 1876, just outside Bradford, Pennsylvania, and grew up in Prospect, Pennsylvania. Biographer Alan Levy wrote that Waddell was "a decidedly different sort of child". At the age of three, he wandered over to a local fire station and stayed there for several days. He did not attend school very often. He was left-handed and strengthened his arm as a child by throwing rocks at birds he encountered while working on his family's land. He also worked on mining and drilling sites as a youngster, which helped his conditioning.

Waddell's career wound through a number of teams. He was notably unpredictable; early in his career, he once left in the middle of a game to go fishing. He also had a longstanding fascination with fire trucks and ran off the field to chase after them during games on multiple occasions. He would disappear for months at a time during the offseason, and it was not known where he went until it was discovered that he was wrestling alligators in a circus. He was easily distracted by opposing fans who held up puppies, which caused him to run over to play with them, and shiny objects, which seemed to put him in a trance. An alcoholic for much of his short life, he reportedly spent his entire first signing bonus on a drinking binge; as a pun of the baseball term "southpaw" denoting a left-handed pitcher, the Sporting News dubbed him a "sousepaw". His eccentric behavior led to constant battles with his managers and scuffles with bad-tempered teammates.

Waddell's first professional contract was for $500 with Louisville, where he pitched two league games and a couple of exhibitions with the team at the end of the 1897 season. When the season ended, he was loaned to the Detroit Tigers of the Western League to gain professional experience. After defaulting on rent and being fined by owner George Vanderbeck, he left Detroit in late May to pitch in Canada before eventually returning to Homestead, Pennsylvania, to pitch semi-pro baseball there. However, Louisville retained his rights and he was lent to Columbus of the Western League in 1899, continued with them when the franchise moved to Grand Rapids mid-season, and finished with a record of 26–8. He rejoined Louisville in the final month of the 1899 season and won seven of nine decisions. When the National League (NL) contracted to eight teams for the 1900 season, Louisville ownership bought the Pittsburgh franchise and the Louisville franchise was terminated. Louisville's top players, including Waddell, Honus Wagner, and Fred Clarke, were transferred to Pittsburgh.

Waddell debuted with the Pittsburgh Pirates in 1900, leading the National League in earned run average. However, his erratic behavior led manager Fred Clarke to suspend him. After he pitched in semi-pro ball in small towns such as Punxsutawney, Milwaukee Brewers manager Connie Mack learned of his availability. With Pittsburgh's approval, Mack convinced Waddell to pitch for Milwaukee for several weeks in the summer of 1900. Milwaukee was in the newly named American League (AL), formerly known as the Western League, which was not yet directly competing with the NL. On August 19, Waddell pitched the first game of a doubleheader for Milwaukee, winning in the 17th inning on his own triple. Mack offered Waddell a three-day fishing vacation if he agreed to pitch the second game. After Waddell threw a complete-game shutout for the victory, he headed to Pewaukee Lake to go fishing. Pittsburgh's management quickly recognized Waddell's talent and asked for his return.

Waddell had worn out his welcome in Pittsburgh by 1901, and his contract was sold to the Chicago Cubs, then managed by Tom Loftus. Despite his previous successes managing Waddell in Columbus/Grand Rapids, Loftus was not given the latitude to cope with Waddell's problems as the Cubs manager. When problems led to his suspension, Waddell left the Cubs to pitch for semi-pro teams in northern Illinois, as well as Racine and Kenosha, Wisconsin. Frank Chance and Joe Cantillon then invited Waddell to join a barnstorming team that traveled to California, where he was persuaded to stay and joined the Los Angeles Loo Loos in a league that a year later would become the Pacific Coast League.

Connie Mack, then in Philadelphia, was desperate for pitching; when he learned that Waddell was pitching in California, he dispatched two Pinkerton agents to sneak Waddell back to Philadelphia, where he led the Philadelphia Athletics to the 1902 American League crown. Much later, Mack described Waddell as "the atom bomb of baseball long before the atom bomb was discovered". On July 1, 1902, Waddell became the second major-league pitcher to throw an immaculate inning, striking out all three batters on nine total pitches in the third inning of a 2–0 win over the Baltimore Orioles (the present-day New York Yankees).