Longmire wasn't due to come out of contract until the end of 2017 but the new deal will see him in charge at the Swans until the end of 2020 at least.

The 45-year-old currently sits third on the Swans' all-time games coached list with 138, behind Paul Roos (202) and Rodney Eade (152).

But with another four years in charge after this season, Longmire should comfortably overtake that pair.

The former North Melbourne premiership player is already one of the club's most successful coaches, having guided them to two grand finals, a premiership and 13 finals. Roos is the only man that has overseen more finals at the club (16).

And with the Swans sitting pretty in second spot with seven rounds to go, Longmire is well-placed for more success this season as he aims to become the first multiple premiership-winning mentor in the history of the club.

Sydney football manager Tom Harley hailed Longmire's re-commitment.

"John's existing agreement had been due to expire at the end of 2017, so it's terrific to finalise a new deal now to provide us with stability going forward," Harley said.

"There's no question that John's leadership has been a key ingredient in our team's performance – he drives high standards right across the football club.

"Already this season we have blooded six AFL debutants. We firmly believe John is the best person to guide our young players and coach our team, as our list and the demands of the competition continue to evolve."

Sydney chairman Andrew Pridham said Longmire has demonstrated outstanding coaching credentials.

"John's remarkable record as both a player and coach speaks for itself – he is highly regarded and much respected by everyone at the Swans, and indeed, right across the AFL," Pridham said.

"What John brings to our team is a tremendous work ethic, strong values and a genuine care for those he works with. His vision for our football club has already yielded great results and we look forward to him leading our team to future success."

Longmire took over the reins from Roos at Sydney ahead of the 2011 season.

Longmire played 200 games and kicked 511 goals for North Melbourne between 1988 and 1999 to be that club's second greatest goalkicker of all time behind only the great Wayne Carey (671).