The nickname of the students and the athletic teams is the "Giants", and their teams compete in Indiana's North Central Conference. The school is best known for its great basketball teams, winning seven state championship titles, 2nd best in over 100 years of Indiana history.
These state championships include back-to-back titles in 1975 and 1976 and also a three-peat in 1985, 1986, and 1987. From 1975 to 1987 the Marion Giants dominated Indiana High School basketball with five state championships and two semi-state appearances and three Indiana Mr. Basketball award winners.
The only high school with more state championships than Marion's seven is conference rival Muncie Central with eight.
Former Marion basketball coach Bill Green holds the state record with six state championships.