Henry Callahan (1957–1982) was a player and ambassador of Ultimate and helped bring the sport to the University of Oregon, formally establishing a team in 1978. In 1982 he was murdered during a robbery while working in Boulder, Colorado. Both The Callahan Award, given each year to the best male and female college Ultimate players, and the Callahan Rules of Ultimate are named after him.
There is also a move named after Callahan in Ultimate called a Callahan. A Callahan is when a defensive player intercepts the disc in the opponent's end zone for a point. It is a rare occurrence, because it requires a defender to intercept, rather than simply block, a pass in the offense's own end zone. Under normal circumstances, the offense does not start a possession within their own end zone, so opportunities for a Callahan are limited to situations where the offense has been forced into their own end zone (either by a good pull or defensive pressure) or backward passes near the end zone. The move is so called because it was first legalized as a goal (rather than needing to be put into play from the goal line) in the Callahan version of the rules, which differed from the Ultimate Player Association's current rules at the time. The rules were subsequently changed in both the UPA (now USA Ultimate) and the World Flying Disc Federation to make a Callahan a legal goal under all rule sets used for Ultimate.
Henry Callahan was also a disc golf player and his family donated money to have a memorial disc golf course installed at Bevier Park in Waukegan, Illinois. This nine hole course was completed in 1992. In 2008 this course was expanded to 18 holes with some holes in Henry Callahan Memorial Park across the street from the original course and park under the direction of the Waukegan Park District with cooperation from Discontinuum Disc Golf Club.