Prince Charles' wife, Camilla, became a grandmother as her son's wife gave birth to a girl.
The Duchess of Cornwall's son, Tom Parker Bowles, and his wife, Sara Buys, have named their daughter Lola.
"The Duchess is absolutely thrilled," a spokeswoman for the prince's Clarence House office said on condition of anonymity in line with palace policy.
Parker Bowles, who is a food writer, and Buys, a fashion columnist, married in 2005.
Prince Charles is Parker Bowles' godfather as well as his stepfather.