Prince William and Duchess Catherine have named their baby son Prince Louis Arthur Charles.

The royal couple - who are already parents to Prince George, four, and two-year-old Princess Charlotte - welcomed their third child into the world on Monday (23.04.18) and have now announced his name following days of speculation.

Kensington Palace announced in a statement: ''The Duke and Duchess of Cambridge are delighted to announce that they have named their son Louis Arthur Charles.

''The baby will be known as His Royal Highness Prince Louis of Cambridge.''

The youngster takes one of his names from his grandfather, Prince Charles.

News of the birth of the couple's third child was revealed on Twitter on Monday afternoon, in a statement from Kensington Palace.

It read: ''Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 1101hrs.

''The baby weighs 8lbs 7oz.

''The Duke of Cambridge was present for the birth.

''Her Royal Highness and her child are both doing well.

''The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news.''

On Monday evening, 36-year-old Catherine - who also has four-year-old Prince George and two-year-old Princess Charlotte with Prince William - left St Mary's hospital in Paddington, London, and was pictured outside the ward with her 35-year-old spouse and their new arrival.

Meanwhile, Prince William thanked the medical staff who helped deliver his son.

A separate statement read: ''Her Royal Highness The Duchess of Cambridge will be leaving St. Mary's Hospital this evening. The Duke and Duchess of Cambridge and their son will travel home to Kensington Palace.

''Their Royal Highnesses would like to thank all staff at the hospital for the care and treatment they have received. They would also like to thank everyone for their warm wishes.''