Nielsen may refer to:

• Nielsen Gallery, an American commercial art gallery
• Nielsen Holdings, global information, data, and measurement company
  • Nielsen Corporation, a marketing research firm
  • Nielsen Audio, formerly Arbitron, which measures radio listenership
  • Nielsen Broadcast Data Systems, a service also known as BDS that tracks monitored radio, television, and internet airplay of songs
  • Nielsen Media Research, the company that creates the Nielsen ratings
    • Nielsen ratings, a rating system used to gauge audience measurement of television programming habits in the United States
• Nielsen Norman Group, a computer user interface and user experience consulting firm

• Nielsen (surname), including a list of people
• Nielsen (crater), a lunar impact crater on the Oceanus Procellarum
• Nielsen–Olesen vortex, a point-like object localized in two spatial dimensions or a classical solution of field theory with the same property
• Nielsen fixed-point theorem
• Nielsen Fjord
• Nielsen Glacier
• Nielsen Park She-Oak

• Neilsen (disambiguation)
• Neilson (disambiguation)
• Nielson
• Nilsen
• Nilsson