Meghan Markle will also be joining the Queen and other members of the royal family at Sandringham, the Queen's private estate in Norfolk, on Christmas Day.
American Meghan Markle intends to become a British citizen, the palace says.
The Queen and Duke of Edinburgh said they were "delighted" for their grandson and his bride-to-be, and "wish them every happiness".
But Harry and his fiancee's choice avoids the issue of whether the royal celebration should be a bank holiday.
The royal family will pay for the wedding, including the church service, the music, the flowers and the reception, the palace said. This breaks the tradition of royal weddings, which usually take on weekdays- the Queen got married on a Thursday and the Duke of Cambridge on a Friday.
The couple - who have been dating since mid-2016 - announced their engagement a few weeks ago after Harry, 33, proposed to Meghan during a "cosy night" in. We are certainly excited to get more detail on the what would be the biggest event of next year.
It is not yet known if the ceremony will be conducted by the Archbishop of Canterbury.
Prince Harry and the actress had announced their engagement in November. The wedding was strategically set before the birth of Prince William and Kate Middleton's third child, due in April 2018.