MOSI may refer to:
- MoSi — molybdenum silicide, an important material in the semiconductor industry
- MOSI - Master Out Slave In, a signal on the Serial Peripheral Interface Bus
- MOSI protocol, an extension of the basic MSI cache coherency protocol
- MOSI / Multi-Option Systems, Inc., an Omaha-based software development and contracting company
- Museum of Science and Industry (disambiguation), a name given to various museums around the world