The Most Rev Bishop Michael Curry, the leader of the US Episcopal Church, has been chosen to speak at the ceremony while Archbishop of Canterbury Justin Welby will marry the couple
The Episcopal Church is an offshoot of the Church of England in the US and forms part of the broader Anglican Communion worldwide.
Ms Markle was baptised by Mr Welby ahead of her wedding to the prince, whose grandmother, the Queen, is head of the Anglican Church.
Prince George and Princess Charlotte are among the six bridesmaids and four pageboys.
Mr Curry said the marriage is significant in the sense that "different worlds are being brought together" but he added that we are "part of God's family", saying: "In a sense it's different and in a sense no, it's being who we are."
Mr Curry said: "My prayer really is that the sermon will be a word of hope, be a word about Jesus Christ and the love of God that he has shown us how to live in our lives, and change the world by doing that. That's my prayer."
The preacher said he felt "genuinely excited and hopeful and prayerful".
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