Britain's Prince Louis of Cambridge will be christened on July 9, Kensington Palace says.

The statement said: "Their Royal Highnesses The Duke and Duchess of Cambridge are pleased to announce that the christening of Prince Louis will take place on Monday July 9 at The Chapel Royal, St James's Palace, London.

"Prince Louis will be christened by The Archbishop of Canterbury, the Most Reverend Justin Welby."

The Duke and Duchess of Cambridge are pleased to announce that the christening of Prince Louis will take place on Monday 9th July at The Chapel Royal, St James’s Palace, London.

Prince Louis will be christened by The Archbishop of Canterbury, the Most Reverend Justin Welby. pic.twitter.com/aBGNYTMRri

— Kensington Palace (@KensingtonRoyal) June 20, 2018

Eight-week-old Louis, a younger brother to Prince George and Princess Charlotte, is fifth in line to the throne and a great-grandchild of the Queen and the Duke of Edinburgh.

Louis was born at the private Lindo Wing of St Mary's Hospital in London on April 23.

Unlike brother George, four, and sister Charlotte, three, the baby prince did not attend May's wedding of his uncle Prince Harry to his American wife Meghan.

AAP