In a transfer believed to be worth close to $2.5 million, Matthews, 20, becomes the most expensive defender in the history of Australian football.
Only Bayern Munich forward Nestory Irankunda and Celtic winger Marco Tilio have been sold overseas for larger fees.Â
Matthews' transfer caps a rapid climb from the fringes of Sydney's squad to a maiden Australia cap late last year.
Hayden Matthews warms up after being selected for the Socceroos in November. (James Ross/AAP PHOTOS)
Matthews only made his starting A-League Men debut in February last year, but has gone on to become an ever-present under Sky Blues boss Ufuk Talay.Â
"I'm incredibly excited to join Portsmouth FC and take the next step in my career," Matthews said.
"Sydney FC has been like a second family to me - they've given me the opportunity to chase my dream of becoming a professional footballer and playing in Europe, and I'll always be grateful for that."
The defender's fine form was rewarded with a maiden Socceroos call-up in November, with Matthews winning his first cap in a 2-2 draw with Bahrain.
Hayden Matthews denies the Jets a certain fourth goal! 🤯— Isuzu UTE A-League (@aleaguemen) An incredible block from the 19-year-old @SydneyFC defender! �Tune in on Paramount+ and 10 BOLD 📺#NEWvSYD #ALM pic.twitter.com/PWI8ahRtMWApril 7, 2024
"Hayden has been a credit to Sydney FC both on and off the field," Talay said.
"This move is a testament to his hard work, talent and determination.
"While we're sad to see him go, we're incredibly proud of what he's achieved.
"His departure also opens up opportunities for other players within our squad, and we hope to announce a replacement or two for Hayden very soon."
Matthews, who missed Sydney's 2-0 loss to Melbourne Victory last Friday to travel to the UK, will be surrounded by plenty of familiar faces at Portsmouth.
The defender has signed a four-year deal and will play alongside Australian striker Kusini Yengi, left-back Jacob Farrell and attacker Thomas Waddingham, who signed with Pompey from Brisbane Roar last week.
Waddingham scored on his debut in a 5-1 loss to West Bromwich Albion last weekend that leaves Portsmouth just one place clear of the Championship drop zone.
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