HMI can refer to:
- Hahn-Meitner-Institut, a research institut in Berlin, Germany, now called Helmholtz-Zentrum Berlin
- Hammond–Whiting (Amtrak station), an Amtrak station in Indiana, United States, with the code HMI.
- Helioseismic and Magnetic Imager, an instrument that studies the magnetic fields of the Sun on the SDO spacecraft.
- The Henry Moore Institute.
- Her Majesty's Inspector, a school inspector employed by Ofsted in England.
- Her Majesty's Inspectorate of Education, the Scottish standards authority for public schools
- Hetrick-Martin Institute, a social service agency for lesbian, gay, bisexual and transgender youth and home of the Harvey Milk High School
- High Mountain Institute, an educational nonprofit in Leadville, Colorado
- Himalayan Mountaineering Institute, an institute in Darjeeling, India
- Himpunan Mahasiswa Islam or Muslim Students' Association (Indonesia), an Islamic association consisting of university students in Indonesia.
- Holistic Management International, a not-for-profit that teaches and promotes holistic land management.
- Human machine interface, the interface handling the human-machine interaction.
- Human-machine interaction, the interaction between humans and machines (often computers).
- Hydrargyrum medium-arc iodide lighting, a type of illumination used in the film industry, for stage lighting and large image projection.