A university-preparatory school or college-preparatory school (also known as tertiary preparation and usually abbreviated to preparatory school, college prep school, tertiary prep, or prep school) is a secondary school, usually private, designed to prepare students for a college or university education. Some schools will also include a junior, or elementary school. This designation is most common in North America.

In many parts of Europe, such as Germany, the countries of former Austria-Hungary, the Netherlands and Scandinavia, secondary schools specializing in college-preparatory education are called gymnasia and/or in some countries athenaea. College prep schools are usually a secondary school along with work for a host school, to help get into a desired college. Most students attend a college-preparatory school but also accomplish the host school's work for a high school diploma.

College preparatory schools in the United States and Canada, commonly referred to as prep schools, are private independent secondary schools, funded by tuition fees and philanthropic donations and governed by independent boards of trustees. Prep schools may be day schools or boarding schools, or both, and may be co-educational or single-sex; however in both the United States and Canada, day schools are more common than boarding, and co-educational schools are more common than single-sex.