NSG may stand for:
- Natation Sportive Geneve
- National Seminars Group
- National Service Group, Inc
- National Street Gazetteer (UK)
- Navigators Studentenvereniging Groningen
- Netherlands Research School of Sedimentary Geology
- Network Services Group
- Network Support Group
- Network Systems Group
- Netzwerk-Service GmbH
- Niels Steensens Gymnasium
- Nippon Sheet Glass
- North Sea Gas
- Northwest Source Group
- Nuclear Suppliers Group (in the CIA World Factbook)
- Nursing Specialist Group