- Dec 10 Maja Stark, Swedish golfer (Chevron C'ship 2024 runner-up), born in Abbekås, Sweden
- Dec 16 Ethan Dolan, American Vine and YouTube star with twin brother Grayson, born in New Jersey
- Dec 16 Grayson Dolan, American Vine and YouTube star with twin brother Ethan, born in New Jersey
- Dec 17 Holly Humberstone, English singer-songwriter ("The Walls Are Way Too Thin"), born in Grantham, England
- Dec 27 Brock Purdy, American football quarterback for the San Francisco 49ers, born in Queen Creek, Arizona
About December 1999
How Old? 24 years old
Generation: Generation Z
Leap Year: No
Chinese Zodiac: Rabbit
Star Signs: Sagittarius (Nov 22 - Dec 21), Capricorn (Dec 22 - Jan 19)
Greatest Generation
Silent Generation
Baby Boomer
Generation X
Millennial
Generation Z