In baseball, a captain is an honorary title sometimes given to a member of the team to acknowledge his leadership. In the early days of baseball, a captain was a player who was responsible for many of the functions now assumed by managers and coaches, such as preparing lineups, making decisions about strategy, and encouraging teamwork. In amateur or youth baseball, a manager or coach may appoint a team captain to assist in communicating with the players and to encourage teamwork and improvement.
Major League Baseball's official rules only briefly mention the position of team captain. Official Baseball Rule 4.03 Comment (formerly Rule 4.01 Comment) which discusses the submission of a team's lineup to the umpire, notes that obvious errors in the lineup should be brought to the attention of the team's manager or captain.
In Major League Baseball, only a handful of teams have designated a player as captain in recent years, and there are no current team captains. Jerry Remy, who was named as captain of the California Angels in 1977 at age 24, explains that in today's modern age of baseball, "there's probably no need for a captain on a major league team. I think there are guys who lead by example. You could name the best player on your team as captain, but he may not be the guy other players will talk to or who will quietly go to other players and give them a prod." Baseball captains generally do not wear an NHL-style "C" on their jersey. Retired first baseman Mike Sweeney, former captain of the Kansas City Royals from 2003 to 2007, wore the "C" patch, as did two other recently retired captains: John Franco and Keith Hernandez of the New York Mets, and Jason Varitek of the Boston Red Sox.
In the 19th and early 20th century, the captain held most of the on-field responsibilities that are held by managers and coaches in modern baseball. For example, according to the 1898 official rules, the captain was responsible for assigning the players' positions and batting order, for appealing to the umpire if he observed certain violations (for example, if the other team intentionally discolored the ball or its players illegally left the bench), and for informing the umpire of any special ground rules. During a period when teams didn't carry full-time coaches, the captain and one or more other players could serve as "coachers" of the base runners; the lines setting off the section where they were allowed to stand were designated as "captain's lines." If the umpire made a decision that could "be plainly shown by the code of rules to have been illegal", the "captain alone shall be allowed to make the appeal for reversal." The rules state that the captain must be one of the nine players, implying that a non-playing manager would not have been allowed to act in the captain's role. In contrast with modern baseball, the 1898 rules do not mention the managers having any rights to interact with the umpires. The rules allowed managers to sit on the team's bench during the game, but were otherwise silent with respect to rights and responsibilities of managers.
In early baseball, many teams had playing managers who had both the off-field responsibilities of managers and the on-field responsibilities of captains. They held the title of "manager-captain." In contrast, teams that had non-playing managers hired a player to serve as captain. For example, in early 1902 Jack Doyle was signed as captain and first baseman of the New York Giants while non-player Horace Fogel was manager.
Though the role of a captain has been significant in the histories of teams such as the New York Yankees, the Boston Red Sox, and the San Francisco Giants, other teams, such as the Milwaukee Brewers, have, as of 2020, never had a captain.