Janssen may refer to:
Astronomy Janssen (lunar crater) Janssen (Martian crater) Janssen (planet), an exoplanet also known as 55 Cancri e
Other Janssen (surname) is a common Dutch surname, cognate of "Johnson" Janssen Pharmaceuticals, a Belgian company Janssen Biotech, an American subsidiary Janssen COVID-19 vaccine , World War II US Navy destroyer escort E. Janssen Building, a historic building in Eureka, California
See also Jansen (disambiguation) Jannsen Janssens