The World Is Not Enough actress - who has two daughters, Lola, six, and seven-year-old, Sam with former husband Charlie Sheen - has named the American tot Eloise Joni after her mother, who died from cancer in 2007.
A representative for Richards said: "Eloise Joni Richards is named after Denise's mom (Joni) and Denise and her daughters Sami and Lola chose the name Eloise.
Denise and Eloise's big sisters couldn't be happier and feel incredibly blessed."
The star added on Twitter: "Thank you all for your sweet messages. The girls and I are over the moon and so is my dad Grandpa Irv . xo. (sic)"
The actress also changed her profile on the micro-blogging site to read: "Actress, single mom of three adorable daughters, animal lover, some say I'm a good cook, and I'm always up for trying something new."
Ironically, Richards, Sheen and their children were staying in the Eloise suite at New York's Plaza Hotel last year when panicked porn star Capri Anderson called police after Sheen - who was drunk and had been taking cocaine - began smashing up his room after accusing Anderson of stealing his wallet and cell phone.
Richards and the girls were staying in a separate room.