Jakob Nielsen may refer to:
- Jakob Nielsen (mathematician) (1890–1959), Danish mathematician known for automorphisms surfaces work
- Jakob Nielsen (usability consultant) (born 1957), Danish web usability consultant
- Jacob Nielsen, Count of Halland (died c. 1309), great grandson of Valdemar II of Denmark
- Jakob Ahlmann Nielsen (born 1991), Danish footballer
- Jakob Axel Nielsen (born 1967), Danish lawyer and politician
- Jacob Nielsen (business), Norway (1768-1822)