His addition to the Bulldogs side will significantly boost their pack after losing forwards Corey Harawira-Naera (contract terminated) and Joe Stimson (injured) from their starting side in 2020.
“Getting the chance to join the Bulldogs and be a part of a club with so much history and with such passionate fans is very exciting,” Thompson said.
“Having spoken to many people at the club and listened to their plans for the future, I know that they are building for success and I’m looking forward to being part of that.”
St Helens had fought hard to keep him, and in a club statement chairman Eamonn McManus said: “St Helens had been placed in a difficult position as Luke Thompson had opted not to participate in our club-wide squad and staff pay reduction arrangement for the 2020 season.
“It was therefore agreed to be in everyone’s best interests for the transfer to take place now rather than at the end of the season as originally planned.”
Any transfer fee paid to St Helens does not count on the Bulldogs’ NRL salary cap, but goes into their football department spend.