- Sep 3 1940 Olympic site is changed from Tokyo, Japan to Helsinki, Finland because of the Second Sino-Japanese War; WWII causes eventual cancellation
- Sep 5 International Lawn Tennis Challenge, Philadelphia, PA: US retain title as Don Budge beats Australian Adrian Quist 8-6, 6-1, 6-2 for unbeatable 3-1 lead; ends 3-2
Baseball Hall of Fame
Sep 13 Alexander Cartwright is inducted into the Baseball Hall of Fame
- Sep 16 British racing driver George Eyston sets world auto speed record at 357.5 MPH
- Sep 18 Chicago Bears beat Green Bay Packers 2-0
- Sep 18 Despite losing a double header (4-3, 8-7) to the St. Louis Browns at Sportsman's Park III, the New York Yankees clinch their 10th AL pennant
- Sep 24 US National Championship Men's Tennis, Forest Hills, NY: Don Budge beats fellow American Gene Mako 6-3, 6-8, 6-2, 6-1 to become first player to win a Grand Slam
US Open Women's Tennis
Sep 24 US National Championship Women's Tennis, Forest Hills, NY: American Alice Marble wins her second US singles crown; beats Nancye Wynne Bolton of Australia 6-0, 6-3
- Sep 28 Homer in the Gloamin' - famous walk-off home run hit by Gabby Hartnett of the Chicago Cubs against the Pittsburgh Pirates
Baseball Players
Basketball Stars
Boxers
Footballers
NFL Stars
Tennis Champions