- Dec 1 Sun Yang, Chinese swimmer (Olympic gold 400m, 1,500m 2012, 200m freestyle 2016), born in Hangzhou, Zhejiang, China
- Dec 2 Chloé Dufour-Lapointe, Canadian alpine freestyle skier (World C'ship gold dual moguls 2013), born in Montreal, Quebec
- Dec 2 Charles Otto "Charlie" Puth (Jr.), American singer-songwriter (Voicenotes; "Marvin Gaye"; "See You Again"), born in Rumson, New Jersey
- Dec 6 CoCo Vandeweghe, American tennis player (US Open doubles 2018; US Federation Cup 2017), born in Rancho Santa Fe, California
- Dec 12 Daniel Magder, Canadian actor (The Famous Jett Jackson), born in Toronto, Ontario
- Dec 13 Jay Greenberg, American composer, born in New Haven, Connecticut
- Dec 14 Offset [Kiari Cephus], American rapper (Migos), born in Lawrenceville, Georgia
- Dec 15 Eunice Cho, American actress
- Dec 19 Declan Galbraith, British pop singer ("Tell Me Why"), born in Hoo St. Werburgh Kent, England
- Dec 22 DaBaby [Jonathan Kirk], American rapper and singer-songwriter (Rockstar), born in Cleveland, Ohio
- Dec 24 Louis Tomlinson, English pop singer (One Direction), born in Doncaster, England
- Dec 26 Gabriella Smith, American contemporary classical composer (Forgotten Lullabyes; Bioluminescence Chaconne), born in Berkeley, California
About December 1991
How Old? 29 years old
Generation: Millennial
Leap Year: No
Chinese Zodiac: Goat/Sheep
Star Signs: Sagittarius (Nov 22 - Dec 21), Capricorn (Dec 22 - Jan 19)