Umpire positions (baseball)

Diagram of a baseball diamond

In a baseball game officiated by two or more umpires, the umpire-in-chief (or plate umpire) is the umpire who generally is positioned behind home plate. This umpire is to take charge of the game, call balls and strikes, call fair balls and foul balls short of first/third base, and make most calls concerning the batter or concerning baserunners near home plate. If another umpire leaves the infield to cover a potential play in foul ground or in the outfield, then the umpire-in-chief may move to cover a potential play near second or third base.

The other umpires are called base umpires, as they are commonly stationed near the bases. When two umpires are used, the second umpire is called simply the base umpire. This umpire will make most calls concerning runners on the bases and nearby plays, as well as in the middle of the outfield. When three umpires are used, the second umpire is called the first base umpire and the third umpire is called the second base umpire, even though the first base and second base umpires may occasionally station themselves near second and third base, respectively. When four umpires are used, each umpire is named after the base they are stationed near. Sometimes a league will provide six umpires; then, two are stationed in the outfield and then may be called outfield umpires; this occurs in the Major League Baseball playoffs.

The term umpire-in-chief is not to be confused with the umpiring crew chief or crew chief, who is usually the most experienced umpire in a crew. Crew chiefs began to be designated after the major leagues established a standard crew of at least 3 umpires per game in the early 1930s, and 4 per regular-season game in 1952. Traditionally, an umpiring crew rotates such that each umpire in the crew works each position, including umpire-in-chief, an equal number of games.

The term umpire-in-chief can also refer to the lead umpire in an umpire's association, in a league, or in a family of leagues.