Royal baby Archie!
Also in the photo is Meghan's mother, Doria Ragland, who flew from Los Angeles for the birth of her first grandchild and is staying with the couple at Frogmore Cottage.
The baby will not carry a courtesy title "at this time," according to Buckingham Palace.
Archie would have been given the title The Earl of Dumbarton, or Lord Dumbarton, as the eldest son of Prince Harry had Harry and Meghan consented.
Queen Elizabeth II also had the discretion to grant the newborn the title of prince, based on Harry and Meghan's preference.
The couple did not reveal in their Instagram post details of the meaning behind Archie's name.
Archie is a popular boys' name in the U.K.
His surname of Mountbatten-Windsor is a combination of Queen Elizabeth's surname of Windsor and Prince Philip’s adopted surname of Mountbatten.
Prince Harry's given name is Henry Charles Albert David.
Archie, born May 6 at 5:26 a.m. local time, was introduced to the world by his parents Wednesday in a photo call at Windsor Castle.
"It's magic. It's pretty amazing," Meghan, 37, said as Harry, 34, held their son in his arms. "I have the two best guys in the world, so I'm really happy."
Archie is seventh in line to the throne, behind Prince Charles, Prince William, Prince George, Princess Charlotte, Prince Louis and Prince Harry.
He is also the fourth grandchild for Prince Charles and the eighth great-grandchild for Queen Elizabeth II and Prince Philip, who were the first royals to meet the newborn.
Prince Charles and Camilla, the Duchess of Cornwall, are currently on an official visit to Germany. Archie's aunt and uncle, Prince William and Kate, held an official engagement Wednesday in Wales.
Harry, Meghan and their son are now bonding as a family at their Frogmore Cottage home, a short walk from Windsor Castle.
"He's just been the dream, so it's been a special couple days," Meghan said.
"Parenting is amazing," Harry added. "It's only been, what, two-and-a-half days, three days? But we're just so thrilled to have our own little bundle of joy here to spend some precious times with him as he slowly starts to grow up."