Althoff Catholic High School is a secondary education, Roman Catholic, private school, in Belleville, Illinois, in the Roman Catholic Diocese of Belleville. In 1960, Albert R. Zuroweste, the Bishop of Belleville, met with lay leaders of the Belleville area concerning conditions existing at the Cathedral High School for boys and the Academy of Notre Dame for girls. Since both schools were overcrowded, it was decided that new, co-ed facilities must be provided for students coming in from the area's Catholic grade schools. The high school was dedicated on August 30, 1964, and named in honor of the previous Bishop, Henry J. Althoff. The new high school opened its doors on September 3, 1964.