It comes as a massive blow for Lonie, who grew up around the corner from the club's old Seaford headquarters.
A lifelong Saints fan, his dream came true when selected by the club with pick 41 in the 2014 national draft.
RELATED: Bombers delist defender
The former Dandenong Stingray played a total of 86 games for the club, kicking 73 goals in that time. However, season 2021 saw him kick just four goals from nine games, leading to the Saints not offering him another deal.
"Once drafted to St Kilda, he has never taken his AFL opportunity for granted and has played with a passion, enthusiasm and courage that earned him the respect and friendship of his teammates and warmed the hearts of our supporters and our legion of past players," said Gallagher.
"He should be very proud of what he has achieved at St Kilda and we are very thankful for the seven years he has given to us.
"We wish Jack all the best for the next chapter of his life."
SEE ALSO: Clark opens up on Scarlett
A crafty small forward, who is just as comfortable kicking goals as he is antagonising the opposition, Lonie reportedly had interest from other clubs last off-season.
Turning his back on them to stay with the Saints on a one-year deal. The deal contained a trigger for an added year, however he failed to reach the required number of games.
GWS have been in the market for a small forward this off-season and could offer Lonie a lifeline up North.