The Duke and Duchess' second son was born on Monday at the Lindo Wing of St Mary's Hospital in London.
Long live Prince Louis of Cambridge!
"The baby will be known as His Royal Highness Prince Louis of Cambridge", Kensington Palace said.
The Duke and Duchess of Cambridge have named their third child Prince Louis Arthur Charles of Cambridge, The Telegraph reported. Britain-based betting and gambling company Ladbrokes had Albert (Queen Elizabeth II's father's given name) at 5-1 odds and Arthur (one of Prince William's middle names) at 9-1 odds, People magazine reported that Philip (the prince's paternal great-grandfather's name, which is also one of William's middle names) was also in the running at 16-1 odds. Louis is one of Prince William's middle names and is a middle name of his oldest son, Prince George.
He weighed 8lbs 7oz (3.83kg).
It pays tribute to the Prince of Wales's beloved great-uncle, Earl Mountbatten, who was murdered by the IRA.
The royal couple have two other children, Prince George Alexander Louis, 4, and Princess Charlotte Elizabeth Diana, 2.
He was assassinated by Irish republicans when his boat was blown up on a fishing trip off the coast of County Sligo in the Republic of Ireland.
Prince William has also been confirmed as Harry's best man earlier this week. William also said the newborn was "sleeping reasonably well so far" and that "he's behaving himself, which is good news".
The Royal family and the Middleton family have reportedly been informed of the baby's sex, weight and timing of birth.