Matthäi, Matthai are surnames of several origins, all related to local rendering of Matthew. "Matthäi" may also be rendered as Matthaei. Notable people with the surname include:
- Friedrich Matthäi
- George Matthai
- John Matthai
- Pallithanam Luca Matthai
- Ravi J. Matthai
- Sigrid Matthäi, birth name of Sigrid Schmidt, German folklorist
- Stephan Matthai