Walsh, coming off an injury-affected 2025, would have been a free agent at season's end, with Geelong among the clubs keen on luring the hard-running midfielder away from Ikon Park.
But Walsh, 25, has instead taken himself off the table in signing the longest contract in Carlton history.
The former No.1 draft pick joins Melbourne's Kysaiah Pickett and Fremantle's Caleb Serong as the longest-signed players in the competition.
"I love this club. I am a Carlton person and I couldn't be happier to continue my career here," Blues co vice-captain Walsh said in a statement.
"This was obviously a big decision for me, but it was made so much easier because I know we are heading in the right direction.
"I make no secret of the fact that I want to win, and I want to win with the Carlton monogram on my chest.
"I truly believe that the key people we have here, and where our group is at right now, we are seeing a significant shift as we head into this next period of our football club, one that I know is going to be really exciting to be part of.
"When I arrived, our club was last on the ladder.
"Footy isn't a linear experience, everyone knows that, but I am all in on the next eight years and doing everything I can to help us reach the top and stay there - the day we do will mean everything to me."
Walsh, who has averaged 27.4 disposals across his career, was taken with the prized first choice in the 2018 draft and won the AFL Rising Star award in his debut season in 2019.
The midfielder finished fourth in the Brownlow Medal, won Carlton's best and fairest and was All-Australian in 2021 while he won the Gary Ayres Medal for best finals player in 2023.
"We are absolutely delighted to secure Sam's future in the navy blue," Carlton list boss Nick Austin said in a statement.
"To get his signature before the AFL season even starts perfectly sums up the type of player and person he is, and the type of environment we want to be building where our people believe in what they are helping create."
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