James Robert Kalsu (April 13, 1945 – July 21, 1970) was an American professional football player who was an All-American tackle at the University of Oklahoma and an eighth-round selection in the 1968 NFL/AFL draft by the Buffalo Bills of the American Football League (AFL).

[1] Kalsu joined the U.S. Army as an officer after the 1968 season and was killed in action in the Vietnam War in 1970.

[2] Following the 1968 season, to satisfy his Reserve Officers' Training Corps (ROTC) obligation, Kalsu entered the U.S. Army as a second lieutenant and arrived in South Vietnam in November 1969 as part of the 101st Airborne Division.

Kalsu and Steinbrunner were the first professional players to be killed in action since Al Blozis of the New York Football Giants died during World War II in 1945.

Kalsu remained the last professional player to be killed in action until Pat Tillman died in the Afghanistan War in 2004.