The American actress, who will become a senior HRH on marrying into the royals, also intends to become a British citizen.
As the couple make preparations for their big day, Ms Markle, a Protestant who went to a Catholic high school, will be both baptised and confirmed, ready for the religious ceremony.
The royal family will pay for the wedding, including the church service, the music, the flowers and the reception, the palace said.
Harry's communication's secretary Jason Knauf said Windsor was a "very special place" for Harry, and that he and Ms Markle had spent time there together during their 16-month romance.
He said the couple were delighted to be holding the wedding in the "beautiful grounds of Windsor".
Mr Knauf said the couple, who were grateful for the warm wishes from the public, would be putting their stamp on their wedding day.
"They will be making sure it reflects who they are as a couple," he said.
Kensington Palace also revealed that Harry and Ms Markle will carry out their first official engagement together in Nottingham on Friday.