In a letter to the Privy Council, a formal advisory body to the monarch comprised of senior politicians, judges and bishops, the queen confirmed her approval of the wedding of Harry, the fifth-in-line to the throne, and Markle, star of U.S. TV drama "Suits".
"I declare My Consent to a Contract of Matrimony between My Most Dearly Beloved Grandson Prince Henry Charles Albert David of Wales and Rachel Meghan Markle, which Consent I am causing to be signified under the Great Seal and to be entered in the Books of the Privy Council," the letter dated on Wednesday said.
Harry and Meghan's union, like all those of the first six royals in direct line of succession, must be approved by the queen under the 2013 Succession to the Crown Act, which replaced an even more prescriptive law dating back to the 18th Century.
The move was a mere formality as the queen had already said in a statement how delighted she was for the couple and she will be attending the wedding ceremony at her Windsor Castle home, to the West of London, on May 19.
She also invited Markle to spend Christmas with the royal family at her Sandringham estate in eastern England.