Jansen may refer to:
- People
- Jansen (surname)
- Michael (Mike) Jansen, artist
- Theo Jansen, artist
- Mark Jansen, musician
- Cornelius Otto Jansen, priest
- Places
- Jansen, Saskatchewan, Canada
- Jansen, Colorado, United States
- Jansen, Nebraska, United States
- Other uses
- Jansen AG, Swiss company which produces steel and plastic pipes, as well as profiles
- Jansen (crater), on the moon
- Jansen's metaphyseal chondrodysplasia, disease of the parathyroid hormone receptors
- Jansenism, branch of Catholic gallican thought