| 143641 | December 21 | Birth | 1981 – Cristian Zaccardo, Italian footballer |
| 143642 | December 21 | Birth | 1982 – Primo, Puerto Rican and Canadian wrestler |
| 143643 | December 21 | Birth | 1982 – Mike Gansey, American basketball player |
| 143644 | December 21 | Birth | 1982 – Philip Humber, American baseball player |
| 143645 | December 21 | Birth | 1982 – Iljo Keisse, Belgian cyclist |
| 143646 | December 21 | Birth | 1982 – Tom Payne, English actor |
| 143647 | December 21 | Birth | 1983 – Steven Yeun, South Korean-American actor |
| 143648 | December 21 | Birth | 1984 – Andrea Jeremiah, Indian actress and singer |
| 143649 | December 21 | Birth | 1984 – Sarah Mutch, Canadian model and actress |
| 143650 | December 21 | Birth | 1984 – Darren Potter, Irish footballer |
| 143651 | December 21 | Birth | 1985 – James Stewart, Jr., American motorcycle racer |
| 143652 | December 21 | Birth | 1985 – Tom Sturridge, English actor |
| 143653 | December 21 | Birth | 1985 – Kotaro Yanagi, Japanese actor |
| 143654 | December 21 | Birth | 1986 – Davey Browne, Australian boxer (d. 2015) |
| 143655 | December 21 | Birth | 1986 – Rachel Shenton, English actress |
| 143656 | December 21 | Birth | 1987 – Denis Alekseyev, Russian sprinter |
| 143657 | December 21 | Birth | 1987 – Ryza Cenon, Filipino actress and dancer |
| 143658 | December 21 | Birth | 1987 – Valerie Concepcion, Filipino actress |
| 143659 | December 21 | Birth | 1987 – Brad Howard, Australian footballer |
| 143660 | December 21 | Birth | 1987 – Michael Lohan Jr., American actor |
| 143661 | December 21 | Birth | 1988 – Yasmin, English-Scottish singer-songwriter and DJ |
| 143662 | December 21 | Birth | 1988 – Alexa Goddard, English singer |
| 143663 | December 21 | Birth | 1988 – Perri Shakes-Drayton, English sprinter and hurdler |
| 143664 | December 21 | Birth | 1989 – Tamannaah, Indian model and actress |
| 143665 | December 21 | Birth | 1989 – Mark Ingram, Jr., American football player |
| 143666 | December 21 | Birth | 1990 – Ioannis Fetfatzidis, Greek footballer |
| 143667 | December 21 | Birth | 1994 – Eva Paalma, Estonian tennis player |
| 143668 | December 21 | Death | 72 – Thomas the Apostle, Israeli martyr and saint (b. 1 AD) |
| 143669 | December 21 | Death | 882 – Hincmar, French archbishop (b. 806) |
| 143670 | December 21 | Death | 1308 – Henry I, Landgrave of Hesse (b. 1244) |