MUI or Mui may refer to:
- Magic User Interface, system to generate graphical user interfaces
- Multilingual User Interface, Microsoft technology for installing multiple languages on a Windows system
- Majelis Ulama Indonesia, Indonesia’s top Muslim clerical body
- MUI Group, Malayan United Industries
- Muhammad University of Islam, in the area of Chicago
- Mui River, river in Ethiopia
- Mui, Estonia, village in Pöide Parish, Saare County, Estonia
- Mei (surname), Chinese surname
- Kong Duen-yee, known as Mui Yee
- Matter Under Inquiry, a US Secruties and Exchange Commission term used to refer to preliminary investigations into financial crimes.
- Men's Underwear Index, an economic index