James Orlando Harrison Simrall Jr. (November 16, 1909 – September 8, 1982) was an American football player and medical doctor. A native of Lexington, Kentucky, Simrall enrolled at the University of Michigan where he played quarterback and halfback for the Michigan Wolverines football teams from 1928 to 1930. He was selected as the Most Valuable Player on the 1929 team and the captain of the 1930 team. He later attended Harvard Medical School, served as an instructor in obstetrics and gynecology at the University of Michigan, and later became a medical doctor in Lexington, Kentucky.

Simrall was born in Lexington, Kentucky, in November 1909. His father, James O. Harrison Simrall Sr. (1877–1934), was a Kentucky native who worked as the secretary of the city school board, personnel director, and business manager of the public schools, and also operated an insurance agency under the name, J. O. H. Insurance Agency. His mother, Kitty C. (Chenault) Simrall, was also a Kentucky native.

At the time of the 1910 United States census, Simrall was living in Lexington with his parents and an older sister, Florence D. Simrall. At the time of the 1930 United States census, his family continued to reside in Lexington, and he also had a younger sister, Kitty C. Simrall. In high school, Simrall played football and basketball and competed in track.

Simrall enrolled at the University of Michigan in 1927. While at Michigan, Simrall was also a member of the Phi Delta Theta fraternity. In February 1931, Simrall received national publicity when he was one of 70 University of Michigan students arrested in "rum raids" at five leading fraternities on the campus. In March 1931, Simrall was voted as the class athlete and the most popular man in the University of Michigan's Class of 1931.

After graduating from Michigan, Simrall attended Harvard Medical School. He returned to the University of Michigan in 1935 to perform his residency at the University Hospital.

He played on the freshman football team at the University of Michigan in 1927. As a sophomore in 1928, he started five games at the halfback position for the Michigan team coached by Tad Wieman. Before the 1929 season, expectations were high for Simrall. A profile of the Michigan football team in the International News Service (predecessor to the UPI) noted:

The big 'if' is a youngster named Harrison Simrall of Lexington, Ky., who is looked upon as the man to lead the maize and blue cohorts into the promised land. In practice -- at least the one we saw -- he looks like the answer to the coaches' prayer. He can kick, forward pass, and direct play in a manner that leaves little to be desired, and the experience gained last season seems to have ironed out the rough edges of his style.

Following spring practice in 1929, the Detroit Free Press reported that Simrall was "head and shoulders above all other football candidates at Michigan." Simrall started eight games as quarterback in 1929 and another as halfback in Harry Kipke's first season as Michigan's head football coach. He also handled punting for the 1929 team and set an "iron man" record by playing in 488 minutes during the 1929 season.