Niels is a male given name, equivalent to Nicholas, which is common in Denmark and Norway. The Swedish variant is Nils. The name is a developed short form of Nicholas or Greek Nicolaos after Saint Nicholas. Niels may refer to:

• Niels, King of Denmark (1065–1134)
• Niels Aagaard (1612–1657), Danish poet
• Niels Henrik Abel (1802–1829), Norwegian mathematician
• Niels Arestrup (born 1949), French actor
• Niels Viggo Bentzon (1919–2000), Danish composer and pianist
• Niels Bohr (1885–1962), Danish physicist and Nobel Prize recipient
• Niels Busk (born 1942), Danish politician
• Niels Ebbesen (died 1340), Danish squire and national hero
• Niels Feijen (born 1977), Dutch pool player
• Niels Ferguson (born 1965), Dutch cryptographer
• Niels Gade (1817–1890), Danish musician
• Niels Hansen Jacobsen (1861–1941), Danish sculptor
• Niels Helveg Petersen (born 1939), Danish politician
• Niels Hemmingsen (1513–1600), Danish theologian
• Niels Holst-Sørensen (born 1922), Danish athlete and general
• Niels Jonsson Stromberg af Clastorp (1646–1723), Swedish soldier and politician
• Niels Juel (1629–1697), Danish admiral
• Niels Christian Kaldau (born 1974), Danish badminton player
• Niels Kaas (1535–1594), Danish politician
• Niels Kaj Jerne (1911–1994), Danish immunologist and Nobel Prize recipient
• Niels Krabbe (born 1951), Danish ornithologist
• Niels Lauritz Høyen (1798–1870), Danish art historian
• Niels Neergaard (1854–1936), Danish historian and politician
• Niels-Henning Ørsted Pedersen (1946–2005), Danish jazz bassist
• Niels Ryberg Finsen (1860–1904), Danish physician and Nobel Prize recipient
• Niels Schneider (born 1987), Canadian actor
• Niels Treschow (1751–1833), Norwegian philosopher and politician
• Niels van den Berge (born 1984), Dutch politician
• Niels van der Zwan (born 1967), Dutch rower
• Niels van Steenis (born 1969), Dutch rower