The couple has chosen the head of the Episcopal Church - the Most Rev. Bishop Michael Bruce Curry - to give the address at their wedding, Kensington Palace revealed on Saturday.
Curry became the 27th presiding bishop and primate of the Episcopal Church in November 2015. "He's just a delightful human being", said Bishop of Chicago Jeff Lee, Chicago Episcopal Diocese. l The Bishop of Chicago has known Presiding Bishop Curry for years.
Such an important role would... "And so we have fun and pray for them as we speak".
The ceremony on 19 May at St George's Chapel, a 15th-Century church on the grounds of Windsor Castle, is expected to last about an hour. Saint James congregant Hope Smith was interested in the Royal Wedding before, but says now it will be a must-see with the Bishop Curry speaking.
Prince Harry and Markle have yet to meet the high-energy, evangelical preacher, who has been credited with shaking up the face of Episcopalianism, the US-based branch of the global Anglican communion.
Bishop Curry is yet to comment on the news on Twitter. Traditionally, most clergy give addresses at weddings from the Church of England.
He wrote: "I'm thrilled that Prince Harry and Meghan Markle have asked Bishop Michael Curry to preach at their wedding".
Harry and Markle's selection of an American pastor is a break from royal customized.
He is active in social issues including immigration and marriage equality.
He gained fame for his 2012 sermon "We need some insane Christians".
The bishop argued that Jesus was once thought to be of unsound mind and said that Christians need to follow his example. The North Carolinian bishop was the first to bring same-sex marriages to churches in that area.