“I’m very excited to be representing Sydney FC this season and I’m looking forward to my time in the A-League,” de Jong said.

“I see a lot of similarities between Sydney FC and Ajax, they’re both leaders in their league with a reputation for silverware and I want to uphold that here.

“I want nothing more than success and I’ll help the squad in any way to achieve our goals of winning all of the trophies we compete for this season.”

De Jong will wear the No. 22 shirt and Le Fondre No. 9. He is Sydney's second marquee after former Johnny Warren medallist Milos Ninkovic. 

Sydney has yet to decide whether they will fill their fifth and final visa spot, with much depending on how the current line-up performs over the coming weeks.

Club Chairman Scott Barlow hailed the arrival of de Jong: “In Siem, we have recruited a truly world class footballer and we are excited to be able to bring him to Sydney FC.

“He is a player of outstanding pedigree and at the age of 29 still has some of his best football ahead of him.

“We have every confidence that Siem will complement our already strong squad and play a major role for us this season as we look to win all three domestic trophies and have our most successful Asian Champions League campaign yet.”