| St. Pius X High School | |
| City: | Festus |
| State: | Missouri |
| County: | Jefferson |
| Zipcode: | 63028 |
| Religion: | Roman Catholic |
| President: | James Lehn |
| Principal: | Karen DeCosty |
| Ratio: | 14:1 |
| Act: | 22.5 |
| Type: | Private, coeducational |
| Grades: | 9–12 |
| Athletics: | FALL SEASON: Men's Football, Women's Softball, Men's Soccer, Women's Tennis, Cheerleading, Dance, Men's and Women's Cross Country, Women's Volleyball; WINTER SEASON: Women's Basketball, Cheerleading, Dance; SPRING SEASON: Women's Soccer, Men's Tennis, Men's Basketball, Men's Baseball, Men's Golf, Men's and Women's Track & Field |
| Conference: | Jefferson County Athletic Association (JCAA) |
| Accreditation: | North Central Association of Colleges and Schools[1] |
| Mascot: | Sir Lancerlot |
| Team Name: | Lancers |
| Nickname: | StPX |
| Yearbook: | Lance |
| Publication: | Lancer Legend |
| Established: | 1959 |
| Enrollment: | 300 |
| Free Label1: | College Counselor |
| Free Text1: | Mr. Matt Schutte |
| Free Label2: | Athletic Director |
| Free Text2: | Mr. Tilden Watson |
| Homepage: | St. Pius X website |
St. Pius X High School was founded in 1959 to provide a Catholic education for high school students in Jefferson County, Missouri, United States. The only Catholic high school in Jefferson County, St. Pius X is part of the Roman Catholic Archdiocese of Saint Louis.
The course catalog includes courses in digital citizenship, forensic science and a wellness program. 35 hours of college credit dual-enrollment coursework is available through Saint Louis University and the University of Missouri - St. Louis. 102 hours of community service are part of the graduation requirements for each student, along with a capstone project requirement implemented for the class of 2021 and beyond. St. Pius X principal Karen DeCosty is an alumnus of the school, graduating in 1993.
St. Pius X offers the following MSHAA sports and activities: