NOI may refer to:
- Any of the national informatics olympiads used for selection to the International Olympiad in Informatics, including:
- National Olympiad in Informatics, China, a Chinese annual informatics competition
- Nation of Islam, a black American spiritual and political organization
- Net operating income
- Ngozi Okonjo-Iweala, Nigerian politician
- the Nupe–Oko–Idoma languages subgroup of Volta–Niger languages
- the Northern Oscillation Index
Noi can refer to:
- Noi River in Thailand
- Noi (Eros Ramazzotti), an album by the Italian singer-songwriter Eros Ramazzotti
- Noi the Albino, an Icelandic film by director Dagur Kári
- Naie "Noi" Kasahara of The Wallflower
- Noi is the family name for one of the most respected families in Ghana
- Noi is the Thai word for little
- An English term for Snazzy or Groovy.
- Indie rock band from Nashville, TN.
- Club and Radio HDJ Noi from Tampa, FL.
- The Catalan word for boy.