Britain's Prince William and his wife Kate named their newborn son Louis Arthur Charles.

"The Duke and Duchess of Cambridge are delighted to announce that they have named their son Louis Arthur Charles," Kensington Palace said Friday in a statement.

"The baby will be known as His Royal Highness Prince Louis of Cambridge," the statement added.

William and Kate's third child was born Monday, a brother to 4-year-old Prince George and Princess Charlotte, who is almost 3. He weighed 8 lbs 7oz at birth.

Louis is fifth in line to the throne after his grandfather Prince Charles, his father and older siblings.