King Carl XVI Gustaf announced his granddaughter's name, and said the baby girl, who was born Thursday to Crown Princess Victoria and Prince Daniel, will receive the title Duchess of Ostergotland, a province in southeast Sweden.
As Victoria's first-born child, she is second in line to the throne.
Estelle, a name of French origin, is unusual in Sweden and took royal watchers by surprise, though it isn't unprecedented in the royal family, which has French roots. Estelle was the name of the American-born wife of the king's godfather, Count Folke Bernadotte, a U.N. mediator in the Israeli-Arab conflict who was assassinated in Jerusalem in 1948.
Silvia is the name of Victoria's mother and Ewa is Daniel's mother's name.
Mary is not common in the Swedish royal family, but it's the name of Denmark's Australian-born crown princess.
The king didn't explain the reasoning behind the names.
"We have now been given a little Princess Estelle in Sweden and we are all, particularly me and the family, very, very happy and joyful for that," he said.
In an email to The Associated Press, Royal Court spokeswoman Ulrika Nasholm said the couple "has chosen four names that they think are beautiful. Silvia and Ewa are of course after the grandmothers."
Victoria and Daniel returned to their lakeside palace Thursday and have not appeared in public with the child.
The court's Mistress of the Robes, Alice Trolle-Wachtmeister, described the newborn princess as a "spitting image" of her mother Victoria.
Sweden's monarch is primarily a figurehead, representing the country as the head of state but with powers limited to ceremonial functions.
