PREMIERSHIP defender Harrison Petty has been rewarded for an excellent season with a fresh contract, which will see him remain a Demon until at least the end of 2025.

The 21-year-old, who cemented his spot in Melbourne's back six after luckless defender Adam Tomlinson went down with an ACL injury, played 19 matches this year, including the Toyota AFL Grand Final.

Melbourne list manager Tim Lamb said this was an important signing for the club, with Petty playing a crucial role in the Demons' defence.

"We all saw the rate of his development this year and we are really excited to see how far he can take his game," Lamb told Melbourne Media.

"Harrison is a crucial piece of our future and we anticipate him being a key member of our defensive unit for many years to come.

"He is a terrific teammate who is highly respected by everyone and we look forward to watching him continue to develop over the coming seasons.

"To have Harrison commit to the club is brilliant, his performances particularly throughout the finals series were exceptional."

Petty was selected with pick No.37 in the 2017 National Draft.