John F. Sheridan (April 30, 1862 – November 2, 1914) was an American umpire in Major League Baseball.

In contrast to the rowdier NL, where umpires were routinely subjected to great abuse with little backing from the league office, Johnson staunchly defended his field officials and insisted that players and local authorities maintain respect for them.

[7] He became the standard after which other umpires patterned themselves; after arriving in the AL at age 22 in 1906, Billy Evans regularly worked in a team with Sheridan for several years in order to study under the senior umpire, with Sheridan usually working behind the plate and Evans on the bases.

Both Evans and fellow Hall of Famer Bill Klem regarded Sheridan as the game's greatest umpire.

In the winter of 1913–1914, he and Klem were the two umpires accompanying the Chicago White Sox and New York Giants on their world tour.

[13] He suffered sunstroke while umpiring a game at Chicago in August 1914, and never fully recovered from the affliction.

He called his last game on September 24 at Chicago, and despite the pleas of fellow officials insisted on remaining in the city for the crosstown series between the White Sox and Cubs before traveling to his home in California.

Once there, his condition continued to deteriorate until he died three weeks later of a heart attack at age 52, at the San Jose home of his sister.

[14] The day after Sheridan died, the San Francisco Chronicle wrote that he was "the most famous and oldest diamond official before the public and was popular because of his well-known honesty and ability."

Whereas umpires in the 19th century had worked behind the plate in a standing position, believing that it helped them to better observe the flight of the ball, Sheridan established the practice of crouching while calling balls and strikes, a move which was quickly adopted universally due to its effectiveness.