The 25-year-old has inked the three-year extension following a career-best campaign in the AFL, playing 22 games in the blue, white and red in 2022.
Since joining the Bulldogs through the inaugural Mid-Season Draft in 2019, the Tasmanian has played 43 games at senior level, continuing to develop as a lockdown backman.
Gardner failed to feature for Geelong in his four years at Kardinia Park, finding a lifeline at the Kennel and not looking back.
“It's such a great achievement for me personally – I've had a few hiccups along the way, so to be able to get a three-year contract is just an amazing feeling,” Gardner said in a club statement.
“It was a pretty easy option to stay. I didn't really feel like going anywhere else. I really love it here and I think it's the best place for me to be.
“I just want to keep playing good footy and having a say down there in the backline. I'm only 25, so still have so much growth in front of me.
“I want to keep developing and see where it can take me.”
Entering his fifth season at Whitten Oval, Gardner will have his sights on a breakout campaign for the Dogs as they look to return to the premiership race.
Bulldogs list manager Sam Power spoke highly of Gardner's dedication and drive since joining the club, with his new contract just rewards.
Ryan's commitment since walking through the door has been first-class and this new contract is reward for his hard work and persistence,” he said.
“In the space of three seasons, Ryan has become a mainstay of the Bulldogs defence, playing with courage and consistency against the talented forwards of the competition.
“We still believe Ryan has plenty of growth in his football and we're thrilled he has committed to us for the next three seasons.”
Gardner and the Dogs will open their 2023 campaigns against Melbourne at the MCG on Saturday, March 18.