South Sydney forward Angus Crichton has defected to arch rivals Sydney Roosters on a three-year deal from 2019.

Following much interest from rival clubs including Cronulla, the gun back-rower told Rabbitohs officials on Monday morning he had agreed to terms with the Tri-colours.

Outta here: Angus Crichton has defected to rivals Sydney Roosters. Credit:AAP

Crichton is committed to playing out the 2018 season with Souths, who were not prepared to match the Roosters' enormous offer, which is rumoured to be close to $1 million a year.

"The Rabbitohs made a strong three-year offer to Crichton for his services beyond 2018 however he has chosen to take up a more lucrative offer elsewhere," the Rabbitohs said in a statement.