The baby weighs 8lbs 7oz and came after the Duchess underwent over five hours in labour.
"Their Royal Highnesses would like to thank all staff at the hospital for the care and treatment they have received".
However, the child will probably not go by this entire title, as royal historian Marlene Koenig explained, "Royal children are "styled" differently if they are the children of a royal duke".
With beams on their faces, it was the moment the Duke and Duchess of Cambridge presented their third child to the world for the first time.
Today, they were simply a family unit excited to show off their new baby boy.
So far, British bookmakers have listed Arthur as a top pick, with Albert, Philip, and James garnering high rankings as well.
Harry is set at an unlikely 100 to 1 along with Hugo, Casper and Edmund.
When will the name be announced?
Wills and Kate announced the names of George and Charlotte in the afternoon, two days after they were born.
When was Kate's due date?
Meanwhile, Pippa is said to be "utterly overjoyed" at becoming a first time mother and sources say the couple were "trying for a baby".
And while Prince William couldn't contain a smile as they stepped from their auto, it was the young princess who drew the spotlight when she not only waved while they strolled along but then turned and waved to the media as they entered the hospital.
Introducing the newborn outside the Lindo Wing of St. Mary's Hospital is the same step Kate and William took after Kate gave birth to George, in 2013, and Charlotte, in 2015.
"It is a great joy to have another grandchild".
The plates and pillboxes bear the words: "Welcome to our new royal baby".
And there has been some rumours about the couple were expecting twins, which was completely unconfirmed. During the short walk from the auto to the hospital, Charlotte, 2, charmed the crowd with her ideal royal wave as older bro George looked up at the massive crowd briefly before looking down as he walked toward the door.
Their lavish wedding at Westminster Abbey in April 2011 was watched by millions around the world.