Trygve Helgaker (born August 11, 1953, in Porsgrunn, Norway) is professor of chemistry, Department of Chemistry, University of Oslo, Norway.

He is a member of the International Academy of Quantum Molecular Science, 2005.

He has written more than 200 scientific papers, and the book, Molecular Electronic-Structure Theory (Trygve Helgaker, Poul Jørgensen, and Jeppe Olsen, Wiley, Chichester, 2000). He is one of the main authors of the DALTON program.