The countdown to Prince Harry and Meghan Markle’s royal wedding has officially begun.

Prince Harry and the former actress will be married in May 2018 at Windsor Castle’s St. George’s Chapel, Kensington Palace announced on Tuesday. Queen Elizabeth II “granted permission” for the couple’s wedding to take place there.

“The Royal Family will pay for the wedding,” the palace said in a statement.

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Windsor Castle, west of London, is one of Queen Elizabeth II's main residences. The 15th-century chapel is as historic but more intimate than Westminster Abbey, where Harry's older brother William married Kate Middleton in 2011.

Harry’s communications secretary Jason Knauf said the castle is a “very special place” for the couple, as they have spent time there during their 16-month romance, according to the BBC.

Markle will also become a United Kingdom citizen.

Meghan Markle and Prince Harry appear together for the first time after announcing their engagement. (AP)

St. George's Chapel was also where the service of prayer and dedication was held after Harry's father, Prince Charles, and Camilla, Duchess of Cornwall, got married in 2005. Their wedding took place at the Windsor. Harry’s cousin Peter Phillips and Autumn Kelly also wed at the Windsor Castle's chapel in 2008.

The palace also said the prince and the soon-to-be duchess will appear at their first official event together at a Terrence Higgins Trust World AIDS Day charity fair in Nottingham on Friday.

"Prince Harry is looking forward to introducing Ms. Markle to a community that has become very special to him," the palace tweeted.

Meghan Markle's ring was designed by Harry and includes two diamonds from Princess Diana's jewelry collection. (Reuters)

The couple dominated news on Monday after they announced their engagement. They made their first appearance as an engaged couple later in the day, with Markle sporting a ring, designed by Harry, that included two diamonds from the late Princess Diana’s jewelry collection. The main stone was sourced from Botswana.

In their first interview since the engagement news broke, Markle, 36, said they were having an ordinary night and “trying to roast chicken” when Harry got down on one knee

"It was just an amazing surprise," Markle told the BBC. "It was so sweet and natural and very romantic, he got on one knee."

Harry, 33, added, "She didn't even let me finish.”

Prince Harry and Meghan Markle appeared together at the Invictus Games earlier this year. (Reuters)

They detailed their romance, from being set up on a blind date by a mutual friend in July 2016, to camping in Botswana that led to the proposal earlier this month. Harry said he fell in love with the actress “so incredibly quickly” and felt like the “stars were aligned.”

“This beautiful woman just tripped and fell into my life, I fell into her life. I know that she will be unbelievably good at the job part of it as well,” Harry said.

Markle also revealed she is retiring from acting, confirming she won’t return for the eighth season of “Suits.” She added she will be transitioning into the role of being part of the royal family and is “excited” to be working with organizations and engaging with the community.

"I'm excited to really get to know more about the different communities here and smaller organizations that are working on the same causes that I've always been passionate about,” Markle said. "I don't see it as giving anything up. I see it as a change. It's a new chapter."

The Associated Press contributed to this report.