London - His Royal Highness Prince Louis of Cambridge, son of the Duke and Duchess of Cambridge, was baptized in the Chapel Royal at St James's Palace in London on Monday.
Eleven-week-old Prince Louis - whose full name is Louis Arthur Charles - is the third son of Prince William and his wife, Kate.
According to Kensington Palace, the guest list included grandparents Prince Charles and his wife, Camilla, as well as Kate's parents Michael and Carole Middleton, Prince Harry and his wife, Meghan, Kate's sister Pippa Matthews and her husband, James Matthews, and Kate's brother James Middleton.
Members of the Royal Family arrive at St James's Palace for the christening of Prince Louis. pic.twitter.com/3pDk4D898C
The Queen and the Duke of Edinburgh did not attend the ceremony, according to Buckingham Palace.
The decision was not taken due to health concerns, the British news agency Press Association reported, but because of a busy schedule for the Queen, who is expecting a visit from US President Donald Trump this week and will attend celebrations to mark the centenary of the Royal Air Force on Tuesday.
The young prince was baptised by Archbishop of Canterbury Justin Welby. "I'm delighted and privileged to be christening Prince Louis today - a precious child made in God's image, just as we all are," he tweeted.
William and Kate, both 36, have two other children: Prince George, 4, and Princess Charlotte, 3.
Louis is Queen Elizabeth II's sixth great-grandchild and is fifth in line to the throne behind his grandfather, Prince Charles, Prince William, Prince George and Princess Charlotte.