NIA, Nia, or nia may refer to:
Nia (given name), including a list of people and fictional characters
Nia (fitness), a type of aerobic exercise
Nia (charity), a women's aid organisation based in London
NIA, a spanish salsa singer
Nia (fungus), a genus of marine fungi
SS Nia, a French steamship in service 1952–1954
Nia, a principle of Kwanza
Nia (album), a music album by Blackalicious
Project NIA, an American organization supporting youth in trouble with the law
ICAO designator of Nile Air, an Egyptian airline
Nimba Airport, Nimba, Liberia (IATA airport code NIA)
nia, ISO 639-2 and -3 codes for the Nias language
Janjgir Naila railway station (station code: NIA) in Chhattisgarh, India
Acronyms
National Intelligence Agency, former name of the State Intelligence Services (the Gambia)
Nanotechnology Industries Association, an international association of nanotechnology companies
National Immigration Administration, an agency under the Ministry of Public Security in the People's Republic of China
National Immigration Agency, an agency under the Ministry of the Interior in the Republic of China (Taiwan)
National Infrastructure Assessment, published by the UK National Infrastructure Commission
National Indoor Arena, former name of an indoor arena in Birmingham, England, United Kingdom
National Institute of Accountants, the former name until 2011 for the Institute of Public Accountants in Australia
National Institute of Aerospace, an aerospace research institute in the United States
National Institute on Aging, a health research institute in the United States
National Institute of Ayurveda, apex training and research institute in Ayurveda in India
National Intelligence Agency (disambiguation), various governmental organizations
National Intelligence Authority, a United States government authority from 1946 to 1947
National Investigation Agency, the counter-terrorism agency in India
National Iraqi Alliance, a Shi'a Islamist electoral coalition in Iraq
National Irrigation Administration, a Philippine government agency for irrigation development and management
Nature Improvement Area, a UK landscape-scale nature conservation designation
Net income attributable, a concept in the United States tax code related to Individual Retirement Accounts
Net Internal Area, a methodology for measuring building areas for real estate
Neural Impulse Actuator, a peripheral for gaming on Windows computers
New interdependence approach in the theory of international relations
Nigerian Institute of Architects, a professional association in Nigeria
informal acronym for Noi Bai International Airport, Hanoi, Vietnam
Northern Ireland Assembly, the legislature of Northern Ireland
Nuclear Industry Association, the trade association for the UK's civil nuclear industry