Helfrich was head coach of the Ducks for four seasons, leading the team to the first College Football Playoff championship game two years ago. But this season the Ducks faltered with a five-game losing streak and the team finished at the bottom of the Pac-12 North with just two conference wins.
Helfrich was 37-16 record after taking over from Chip Kelly in 2013. He had an $11.6 million buyout on his contract with the Ducks.
Helfirch met with athletic director Rob Mullens on Tuesday night and was told was being dismissed. Helfrich issued a statement saying he was honored to have served at Oregon.
"Plain and simple - we didn't win enough games this season," Helfrich said.