- Dec 2 Cassie Steele, Canadian actress (Degrassi: The Next Generation), born in Toronto, Ontario
- Dec 2 Matteo Darmian, Italian soccer full-back (36 caps; Torino, Manchester United), born in Legnano, Milan, Italy
- Dec 4 Pornanong Phatlum, Thai golfer (British Open 2018 runner-up), born in Khon Kaen, Thailand
- Dec 7 Caleb Landry Jones, American actor and musician (Nitram), born in Garland, Texas
- Dec 7 Kyle Hendricks, American MLB pitcher (Chicago Cubs), born in Newport Beach, California
Nicholas Hoult (34 years old)
Dec 7 English actor (The Favourite; Tolkien; Peter III-The Great), born in Wokingham, England
Taylor Swift (34 years old)
Dec 13 American Grammy and Emmy Award-winning country-pop singer-songwriter ("You Belong To Me"; "Our Song"; "All Too Well"), and Guinness World Record holder, born in Reading, Pennsylvania
- Dec 18 Ashley Benson, American actress
- Dec 18 Ashley Slanina-Davies, English actress (Amy Barnes-Hollyoaks), born in Standish, England
- Dec 18 Emily Atack, English actress, comedian, and television personality (The Inbetweeners, 2008–10; Keith Lemon shows), born in Luton, Bedfordshire, England
- Dec 20 Virgilio Falco, Italian politician
- Dec 21 Mark Ingram Jr., American football running back (Heisman Trophy 2009, U of Alabama; NFL Pro Bowl 2014, 17, 19; New Orleans Saints, Baltimore Ravens), born in Hackensack, New Jersey
- Dec 21 Quinta Brunson, American writer, producer and actress (Abbott Elementary), born in Philadelphia, Pennsylvania
- Dec 22 Jordin Sparks, American singer and American Idol winner, born in Phoenix, Arizona
- Dec 28 Jessie Buckley, Irish actress (The Lost Daughter), born in Killarney, Ireland
- Dec 28 Mackenzie Rosman, American actress, born in Charleston, South Carolina
- Dec 29 Jane Levy, American actress (Zoey's Extraordinary Playlist), born in Los Angeles, California
- Dec 29 Kei Nishikori, Japanese tennis player (11 singles titles, only Japanese player ranked in top 10), born in Matsue, Japan
- Dec 30 Ryan Sheckler, American professional skateboarder
About December 1989
How Old? 34 years old
Generation: Millennial
Leap Year: No
Chinese Zodiac: Snake
Star Signs: Sagittarius (Nov 22 - Dec 21), Capricorn (Dec 22 - Jan 19)
Greatest Generation
Silent Generation
Baby Boomer
Generation X
Millennial
Generation Z