Hamish Hartlett has resisted offers from a number of Victorian-based clubs, re-signing with Port Adelaide until the end of 2021.

Already contracted until the end of the 2016 season, the Power midfielder's new five-year contract extension gives him the longest tenure of any player on Port Adelaide's list.

The 25-year-old was reportedly in high demand from North Melbourne and Richmond, but the South Australian said his future was always at Alberton.

Hartlett revealed that he had turned down long-term, big-money offers to stay in Adelaide.

"It's great to have that security - I never really wanted to go anywhere else," Hartlett said.

"I'm incredibly happy that the footy club has come to the party and I'll be hanging around for a few more years.

"I've been here for a significant amount of time already - I've invested a lot in the footy club and the footy club has invested a lot in me.

"So for them to counter-offer the way they did was really pleasing.

"I'm just pretty thankful to the footy club for doing that."

Hartlett has played 112 AFL games for Port since he was selected fourth overall at the 2008 national draft.

He said that the promise of premiership success, the tight-knit nature of the playing group and a desire to repay the club for helping him cope with the death of teammate John McCarthy in 2012 were key factors in his decision to stay.

"I've been on a long journey with these guys and the job is unfinished," Harlett said.

"The length of the deals was something that pricked my ears up a little bit," he said.

"But it was within two or three days that the club came back with their offer on top of that.

"As soon as they gave me the same sort of security I knew I was always going to stay."

The Power also locked away John Butcher to a one-year deal.

Butcher managed just five games this year to bring his total to 28 across six seasons at the Port Adelaide since being drafted with pick No.8 overall in the 2009 NAB AFL Draft.