The ceremony will take place at The Chapel Royal, St James's Palace, London. The Archbishop of Canterbury, Reverend Justin Welby, will christen the young prince.
Prince Louis will be 10 weeks old at his christening. It's the quickest christening out of all of the Duke and Duchess' children.
His big sister, Princess Charlotte, was christened at St Mary Magdalene church on the Queen's estate in July 2015, two months after she was born.
Prince George's christening took place in the Chapel Royal at St James's Palace in October 2013, five months after he was born. The Archbishop of Canterbury also baptised George and Charlotte.