The 33-year-old won two A-League titles and one premiership with Sydney since joining in 2018 from Bolton.
The club said they were not willing to stand in the way of his desires to join another club.
“Adam has had an unbelievable couple of years with the club and has had a huge influence on our squad,” said coach Steve Corica.
“He has barely missed a minute of football since arriving and has shown true commitment in every second on the pitch; his performances have been second to none.
“To stand in his way would not be just reward for the service he has given us, and we wish him the best.
“We have some good young strikers at the club who deserve their chance and we have already begun the search to replace Adam.”
Sydney FC are set to resume their Asian Champions League campaign in mid-November when they play Shanghai SIPG in a centralised hub in Malaysia.
Le Fondre joined the Sky Blues in August 2018, winning the club’s Golden Boot in both seasons, amassing a 45 goals in 68 games in all competitions.
“I’ve had two fantastic years here at Sydney FC and have cherished every moment of my life in Australia,” he said.
“We’ve had an unbelievable group of players over the last two seasons and a squad of great people. I will miss them all hugely.
“I’d also like to say a massive thanks to the club for considering mine and my family’s future and allowing me to make this move, as well as every single Sydney FC Member for their support during my time at the club. They were amazing and I hope they will remember me fondly.”
The Sky Blues will receive a loan fee for the striker and hope to be able to conclude a deal for a replacement shortly.
