The newborn weighed in at seven pounds and three ounces. The baby was born at 5:26 a.m., local time, according to Buckingham Palace. Harry was at Meghan's side and both mom and baby are "doing well," the palace said in a statement.
The world had been counting down to the birth of baby Sussex. The newest member of the royal family is lower down on the line of succession than his cousins, Prince George, Princess Charlotte and Prince Louis.
Baby boy Sussex is ahead of great uncles Princes Andrew and Edward and great aunt Princess Anne -- the children of Queen Elizabeth II and Prince Philip and siblings of baby Sussex's grandfather, Prince Charles.
The baby falls ahead of them because he is the grandchild of Prince Charles, the firstborn child of the Queen and the heir to the throne.
Likewise, the baby boy falls behind his cousins in the line of succession because they are the children of Prince William, the firstborn child of Prince Charles.
Baby boy Sussex's place in the line of succession would not have changed thanks to an act of Parliament that came when Duchess Kate was pregnant with Prince George, now five-years-old.
The Succession to the Crown Act 2013 states that succession to the throne would be based wholly on birth order, not sex.
Princess Charlotte, 3, was the first beneficiary of the act. She retained her spot in the line of succession when her younger brother, Prince Louis, was born last year.
Baby Sussex will not automatically be a prince, unlike the cousins, who were designated as his or her royal highness and given the title of prince or princess.
The baby's great-grandmother, Queen Elizabeth II, can step in to give him that title, however.