The former Western Sydney Wanderers and Melbourne City star has signed a deal to move permanently to Shanghai SIPG FC immediately, Brighton confirmed overnight.

Mooy joined the English South Coast side last year from Huddersfield and made a massive impact in midfield for the Seagulls, alongside fellow Socceroo Mat Ryan in goal.

He only made some 30-odd appearances for Brighton, but had established himself as a key member of the starting XI, making his exit all the more of a surprise.

Tom Rogic had also been tipped to potentially join Mooy and Ryan at Falmer Stadium from Celtic as part of a player swap deal for Shane Duffy.

Mooy, who only joined the Seagulls on a permanent basis during the January transfer window after moving on loan from Huddersfield following their relegation from the top-flight in 2019, moves on a deal reported to be worth $18 million.

The 29-year-old made 32 appearances for Brighton last season and scored twice to help the club to their best ever Premier League points tally.

Mooy is set make a reported $A180,000 a week and will line-up alongside former Brazil internationals Hulk and Oscar at his new club.

Brighton are well stocked in the midfield areas with Alexis Mac Allister, Steven Alzate and new signing from Liverpool Adam Lallana all pushing for starts.

In the early hours of the morning, Mooy's former club announced his move on social media and followed it with a highlights reel paying tribute to his time at Albion.

“Aaron has been an excellent professional during his time with us. From day one with us he fitted in really well," said Brighton coach Graham Potter.

”It’s a good move for all parties. We have a number of really good players in that position and therefore Aaron goes with our blessing.

“I have really enjoyed working with him, and on behalf of everyone at the club I would like to thank him for his contribution and wish him well for the future.”

Dad of two Mooy, 30 next month, married his long-term Scottish partner Nicola in 2017 and is father to Skye and Max.

The couple enjoyed a rare holiday alone together in Paris earlier this month, and Nicola posted a pic from there on Instagram this week with the caption: "Everything will become a memory so make the most of now."

Shanghai are currently topping the table on an unbeaten run seven games into a revamped Chinese Super League season which has been split into two divisions as a result of the coronavirus shutdown.