This article is about the sports definition, for the American comedy show host, see David Letterman.

In U.S. sports, a letterman is an high school or college athlete who has met a specified level of participation on a varsity athletic team.

The term comes from the practice of awarding each such participant a cloth "letter", which is usually the school's intial or intials, for placement on a "letter sweater" or "letter jacket" intended for the display of such an award. In some instances, the sweater or jacket itself may also be awarded, especially for the intial award to a given individual.

In order to distinguish "lettermen" from other team participants, schools often establish a minimum level of participation in a team's matches in order fo a letter to be awarded. A common threshold in football and basketball is participation in a set level, often half, of all quarters in a season. (To meet this standard in a ten game season, one would have to have participated in at least twenty of the forty quarters played.) In individual sports such as tennis and golf, the threshold for lettering is generally participation in one half or sometimes one third of all matches contested. Frequently, other members of the team who fail to meet requirements for a letter are awarded a certificate of participation or other award considered to be of lesser value than a letter.

This term is not gender-specific; a qualifying participant in women's basketball or other women's sports is properly referred to as a letterman, as would be a qualifying female participant on a co-educational sports team.

In recent decades this concept has been extended to other competitions which are not technically sports, and "letters" are now often awared for participation in events such as band and debate.