- Jan 1 Alok Kapali, Bangladeshi cricket all-rounder (17 Tests; 69 ODIs), born in Sylhet, Bangladesh
- Jan 1 Paolo Guerrero, Peruvian soccer striker (102 caps; Hamburger SV, Internacional), born in Lima, Peru
- Jan 6 A. J. Hawk, American football player, born in Kettering, Ohio
- Jan 6 Sean O'Brien, Australian professional windsurfer, born in Carlow, Republic of Ireland
- Jan 7 Jon Lester, American baseball player, born in Tacoma, Washington
- Jan 8 Jeff Francoeur, American baseball player, born in Atlanta, Georgia
- Jan 12 Scott Olsen, American baseball player, born in Kalamazoo, Michigan
- Jan 14 Mike Pelfrey, American baseball player, born in Wright-Patterson Air Force Base, Ohio
- Jan 15 Megan Jendrick, American swimmer, born in Tacoma, Washington
- Jan 19 Karun Chandhok, Indian racing driver, born in Chennai, India
- Jan 19 Thomas Vanek, Austrian ice hockey player, born in Baden bei Wien, Austria
- Jan 21 Hiroki Yuhara, Japanese rugby union hooker (22 caps; Toshiba Brave Lupus), born in Chiba, Japan (d. 2020)
- Jan 22 Ben Eager, Canadian NHL ice hockey player, 2004-15 (Philadelphia Flyers, Chicago Black HAwks, and 3 other teams), born in Ottawa, Ontario
- Jan 22 Leon Powe, American basketball player, born in Oakland, California
- Jan 22 Maceo Rigters, Dutch footballer, born in Amsterdam, Netherlands
- Jan 23 Arjen Robben, Dutch football player, born in Bedum, Netherlands
- Jan 24 Scott Kazmir, American baseball player, born in Houston, Texas
- Jan 25 Robinho [Robson de Souza], Brazilian soccer forward (100 caps; Santos), born in São Vicente, Brazil
- Jan 26 Luo Xuejuan, Chinese swimmer (Olympic gold women's 100m breaststroke 2004; World C'ship gold x 5), born in Hangzhou, China
- Jan 28 Andre Iguodala, American NBA basketball player, 2004-present (Philadelphia 76ers, golden State Warriors, and 2 other teams), born in Springfield, Illinois
- Jan 30 Jeremy Hermida, American baseball player, born in Atlanta, Georgia
- Jan 31 Jeremy Wariner, American 400m runner, born in Irving, Texas
- Jan 31 Vernon Davis, American football tight end, born in Washington, D.C.
About January 1984
How Old? 40 years old
Generation: Millennial
Leap Year: Yes
Baseball Players
Basketball Stars
Boxers
Footballers
NFL Stars
Tennis Champions