Prince Louis will be around three-months old by the time he is christened at the Chapel Royal in St James's Palace on Monday July, 9.
George, four, was also christened at the Chapel Royal, while three-year-old Charlotte was baptised two months after her birth at the Church of St Mary Magdalene in Sandringham. He also officiated the christenings of Louis' siblings, Prince George, 4, and Princess Charlotte, 3.
Princess Charlotte was christened on 5 July 2015 at St Mary Magdalene Church in Sandringham.
Louis Arthur Charles - to give him his full name - was born on 23 April.More news: Hawks eyeing Luka Doncic with the No. 3 pick
"Prince Louis will be christened by The Archbishop of Canterbury, the Most Reverend Justin Welby". It is a replica of a christening gown made for Queen Victoria's eldest daughter in 1841 and used for generations of royal babies until it wore out.
Louis, the Queen's great-grandson, is fifth in line to the throne.
George's christening at the same venue in October 2013 was an intimate occasion, with only 23 guests attending.
Jessica Bridge of Ladbrokes told the Express: 'As with George and Charlotte, the Duke and Duchess chose close and trusted friends and aides, rather than immediate family members, and the odds suggest that will be the same with little Prince Louis'.
On Tuesday, as the events kicked off, royals like Prince Harry and Meghan Markle took part in the royal procession, being escorted in horse-drawn carriages down the race track.