Silas Joseph Simmons (October 14, 1895 – October 29, 2006) was an American professional baseball player for African-American teams in the pre-Negro leagues era. He became the longest-lived major league player in history, surpassing Red Hoff, who died at age 107 in 1998.

Simmons was a five-foot-ten, left-handed pitcher/outfielder, and began playing for the Germantown Blue Ribbons, a semi-pro team, in 1911. In 1913, the Blue Ribbons became a professional team and were renamed the Homestead Grays, a team that quickly became a Negro leagues powerhouse.

In 1926, Simmons pitched for the New York Lincoln Giants of the Eastern Colored League and appeared in at least one game in 1929 for the New York-based Cuban Stars (East) of the Negro National League. During his career, Simmons played on the same team as Hall of Famer John Henry Lloyd and against Hall of Famers Judy Johnson and Biz Mackey. Simmons ended his baseball career soon after 1929.

Simmons was married in Philadelphia by Rev. John L. Lee on September 15, 1915, to Mary L. "Mamie" Smith (July 19, 1896 – ca. 1944). He and his wife Mary had five children and settled into life as a porter. He later became an assistant manager at Rosenbaum's Department Store in Plainfield, New Jersey. After 29 years of marriage, Mamie died in approximately 1944.

In 1957, Simmons married his second wife, Rebecca Jones (1901 – August 20, 1997).

Simmons worked for R. J. Goerke Co. during the early 1960s, and was among the employees to receive an award for safety.

In 1971, he retired to St. Petersburg, Florida. After 40 years of marriage, Rebecca died at the age of 96 in 1997.

In the fall of 2005, David Allen Lambert, a genealogist at the New England Historic Genealogical Society, alerted fellow baseball historians associated with the Negro leagues, who proceeded to interview Simmons, a link to early baseball. In May 2006, Dr. Layton Revel, founder of Texas-based Center for Negro League Baseball Research, met and interviewed Simmons.