Principia may also refer to:
- Principia (alga), a stem-group coralline alga
- 2653 Principia, an asteroid named after Newton's work
- Principia College, a private four-year college in Elsah, Illinois
- The Principia, a school from early childhood to high school for Christian Scientists in the St. Louis, Missouri area
- The Principia (book), by Emanuel Swedenborg