Oliver H. P. Cowdery (October 3, 1806 – March 3, 1850) was an American Mormon leader who, with Joseph Smith, was an important participant in the formative period of the Latter Day Saint movement between 1829 and 1836. He was the first baptized Latter Day Saint, one of the Three Witnesses of the Book of Mormon's golden plates, one of the first Latter Day Saint apostles, and the Second Elder of the church.