St. Joseph's Academy is a private, all-girls, Roman Catholic, college preparatory high school in Frontenac, Missouri, a suburb of St. Louis. It is operated by the Roman Catholic Archdiocese of Saint Louis. The school is sponsored by the Sisters of St. Joseph of Carondelet.

St. Joseph's Academy was founded as Mother Celestine's in 1840. Mother St. John Fontbonne and the Superior Sisters of St. Joseph were sent from Lyon, France to the territories of Cahokia and Carondelet. Upon their arrival, they opened a convent school.

In 1841, Mother Celestine's moved from the log cabin that it had been founded in to a motherhouse in Carondelet, Missouri. In 1925, the academy moved into Clayton, Missouri along with Fontbonne University. In 1946, the campus became too small for both the high school and the college, so the academy abandoned the city and moved to Frontenac, Missouri. In 1955, the new building opened.

• Kristin Folkl, professional basketball player
• Tisha Terrasini Banker, actress

• School Website