NIR may stand for:
- Near Infrared, infrared radiation of a wavelength near that of red
- Northern Ireland, a region of the United Kingdom
- Northern Ireland Railways
- National Identity Register
- National Internet registry, an organization under the umbrella of a Regional Internet Registry with the task of coordinating IP address allocations and other Internet resource management functions at a national level within a country or economic unit
- Nir, Ardabil, a city in Ardabil Province, Iran
- Nir, Yazd, a city in Yazd Province, Iran
- Nir County, a county in Ardabil Province, Iran
- Nir District, a district in Yazd Province, Iran
- Nir, a Hebrew word meaning "a plowed field", also a common Hebrew first name and surname
- Natural Increase Rate, a demographic metric of population increase