The baby will be seventh in line for the throne when he or she is born.
The news comes after the two attended the royal wedding of Princess Eugenie, as well as their own wedding just five months ago.
"Their Royal Highnesses The Duke and Duchess of Sussex are very pleased to announce that The Duchess of Sussex is expecting a baby in the Spring of 2019," Kensington Palace announced on Monday. "Their Royal Highnesses very much appreciate all of the support they have received from people around the world since their wedding in May and are delighted to be able to share their happy news."
The child of Harry, 34, and Meghan, 37, will be seventh in line for the throne, behind Charles, William, George, Charlotte, Louis and Harry himself.
Expect a lot of people on bump watch for the next couple weeks, as the two just embarked on a 16-day tour of Australia, Fiji, Tonga and New Zealand. The trip starts today in Sydney.
The news quickly took over the top trends on Twitter, with #RoyalBaby, Prince Harry, Meghan Markle and Sussex all getting their own trends. Markle's friend and actress Carey Mulligan also reacted to the baby news while appearing on "TODAY" once it broke -- see all the reactions below, as they range from LOL to "Awww"-worthy.
The next princess/prince of the British Royal Family is also technically eligible to be elected President of the United States, and every season of Game of Thrones has taught me this is the way we will somehow get dragons.#RoyalBaby— Charlotte Clymer🏳️🌈 (@cmclymer) October 15, 2018
I'd love to be the seventh in line to the throne. Never have the pressure of the crown but all the money and privlege is yours. #RoyalBaby— マティグリーン (@MessMattyUK) October 15, 2018
The #RoyalBaby will be seventh in line to throne and if everybody in front abdicates (stranger things have happened in the #royalfamily), he or she will be the UK's first biracial King or Queen #HarryandMeghan— Kate Williams (@KateWilliamsme) October 15, 2018
now that meghan markle is pregnant we all need to emotionally prepare ourselves for the Cutest Child In All Of Human History pic.twitter.com/HsIdvyjCVi— emma lord (@dilemmalord) October 15, 2018
Hell Harry doesn’t hang around! Congratulations both 😊 #RoyalBaby— Dr Alex (@DrAlexGeorge) October 15, 2018
You’ve got to really feel for Tracey Cox, a body language and relationships expert, who yesterday claimed Meghan and Harry are still enjoying the “honeymoon period” and will not bring a Royal child into the world until at least 2021 #RoyalBaby #DailyExpress pic.twitter.com/a1dzVbLLMb— Tim (@forwardnotback) October 15, 2018
Already?! #royalbaby— Elizabeth Windsor (@Queen_UK) October 15, 2018