Mary Elsa Musselman Whitmer (August 27, 1778 – January 1856) was a Book of Mormon witness and the wife of Peter Whitmer Sr. She was born Mary Elsa Musselman in Germany to Jacob and Elizabeth Musselman. She immigrated to Pennsylvania in the late-18th century, where she met and married Peter Whitmer, a farmer, also of German descent. They moved to Waterloo, New York, in 1809, and later purchased a farm in Fayette, New York. They had eight children, Christian Whitmer, Jacob Whitmer, John Whitmer, David Whitmer, Catherine Whitmer Page, Peter Whitmer Jr., Nancy Whitmer, and Elizabeth Whitmer Cowdery.