Orson Pratt Sr. (September 19, 1811 – October 3, 1881) was an American religious leader and mathematician who was an original member of the Quorum of the Twelve Apostles of the Church of Christ (Latter Day Saints). He became a member of the Quorum of the Twelve of the Church of Jesus Christ of Latter-day Saints (LDS Church) and was a leading Mormon theologian and writer until his death.
