Marshall, who grew up in Portland, but played much of his junior football in and around Ballarat joined the Saints via pick 10 in the 2016 National Rookie Draft.

Since debuting against the Swans in Round 18 of the 2017 season, he has gone on to play an additional 77 games in red, white and black. Marshall said he couldn't wait to continue his time as a Saint.

"I love this club and really believe in the direction we're heading," Marshall told saints.com.au

"We've all got big goals for where we want to take this group, with the ultimate success of a premiership at the top of that list.

"I'm really glad that I'll get to be a part of it all for the next few years and just want to continue doing what I can to drive us forward."

The big man's signature will be a welcome signing for the Saints as they strive to push towards the finals with a difficult draw over the coming two months

"We're really pleased to have Rowan commit long-term to the club," the club's head of list management James Gallagher said.

"Rowan made it clear from the beginning of these discussions that his heart was at the Saints and he was keen to stay long term, so we set about going through a process with his management and have arrived at a position where both Rowan and the club are really happy.

"Rowan's influence both on and off the field has really grown over his time at the club and with only 77 senior games under his belt, we are very confident that the best is still to come."