| St. Francis Xavier High School | |
| Native Name: | Xavier High School |
| Streetaddress: | 1600 West Prospect Avenue |
| City: | Appleton |
| State: | Wisconsin |
| County: | (Outagamie County) |
| Zipcode: | 54914-5199 |
| Country: | United States |
| Coordinates: | 44.2489°N -88.4331°W |
| Religion: | Roman Catholic |
| Principal: | vacant |
| Students: | 500 |
| Gender: | Coeducational |
| Type: | Private |
| Grades: | 9–12 |
| Conference: | Bay Conference |
| Team Name: | Hawks |
| Colors: | Blue & white |
| Yearbook: | Xavue |
| Established: | 1959 |
Xavier High School is a private Catholic secondary school in Appleton, Wisconsin, United States, in the Diocese of Green Bay. It was opened in 1959 by the Institute of the Brothers of the Christian Schools (Christian Brothers) and the Franciscan Sisters of Christian Charity (Manitowoc Franciscans). The school was named in honor of St. Francis Xavier, the patron saint of the Green Bay Diocese.
In November of 2024, Xavier principal Mike Mauthe was fired in the wake of a complaint to the Diocese Office of Safe Environment about a failure to comply with the Diocese of Green Bay’s “Our Promise to Protect” policy. (A report was filed with the Appleton Police Department, as required by the state's mandatory reporting laws.) As a result of the investigation into Mauthe, John Ravizza, superintendent of the Diocese' St. Francis Xavier Catholic School System of which the high school is a part, was terminated "because of a failure to meet reporting requirements".[1]