The Long Count Fight, or the Battle of the Long Count, was a professional boxing 10-round rematch between world heavyweight champion Gene Tunney and former champion Jack Dempsey, which Tunney won in a unanimous decision. It took place on September 22, 1927, at Soldier Field in Chicago. "Long Count" is applied to the fight because when Tunney was knocked down in the seventh round the count was delayed due to Dempsey's failure to go to and remain in a neutral corner. Whether this "long count" actually affected the outcome remains a subject of debate.

Just 364 days before, on September 23, 1926, Tunney had beaten Dempsey by a ten round unanimous decision to lift the world heavyweight title, at Sesquicentennial Stadium in Philadelphia. The first fight between Tunney and Dempsey had been moved out of Chicago because Dempsey had learned that Al Capone was a big fan of his, and he did not want Capone to be involved in the fight. Capone reportedly bet $50,000 on Dempsey for the rematch, which fueled false rumors of a fix. Dempsey was favored by odds makers in both fights, largely because of public betting which heavily tilted towards Dempsey.

The rematch was held at Chicago's Soldier Field, and would draw a gate of $2,658,660 (equivalent to $41,474,000 in 2021). It was the first $2 million gate in entertainment history.

Despite the fact that Tunney had won the first fight by a wide margin on the scorecards, the prospect of a second bout created tremendous public interest. Dempsey was one of the so-called "big five" sports legends of the 1920s, and it was widely rumored that he had refused to participate in the military during World War I. He actually had attempted to enlist in the Army, but had been turned down; a jury later exonerated Dempsey of draft evasion. Tunney, who enjoyed literature and the arts, was a former member of the United States Marine Corps. His nickname was The Fighting Marine.

The fight took place under new rules regarding knockdowns: the fallen fighter would have 10 seconds to rise to his feet under his own power, after his opponent moved to a neutral corner (i.e., one with no trainers). The new rule, which was not yet universal, was asked to be put into use during the fight by the Dempsey camp, who had requested it during negotiations. Dempsey, in the final days of training prior to the rematch, apparently ignored the setting of these new rules. Also, the fight was staged inside a 20-foot ring, which favored the boxer with superior footwork, in this case Tunney. Dempsey liked to crowd his opponents, and normally fought in a 16-foot ring that offered less space to maneuver.

William Harrison "Jack" Dempsey (June 24, 1895 – May 31, 1983), nicknamed Kid Blackie and The Manassa Mauler, was an American professional boxer who competed from 1914 to 1927, and reigned as the world heavyweight champion from 1919 to 1926. A cultural icon of the 1920s, Dempsey's aggressive fighting style and exceptional punching power made him one of the most popular boxers in history. Many of his fights set financial and attendance records, including the first million-dollar gate. He pioneered the live broadcast of sporting events in general, and boxing matches in particular.

Dempsey is ranked tenth on The Ring magazine's list of all-time heavyweights and seventh among its Top 100 Greatest Punchers, while in 1950 the Associated Press voted him as the greatest fighter of the past 50 years. He is a member of the International Boxing Hall of Fame, and was in the previous Boxing Hall of Fame.