Stewart missed a hefty chunk of the 2025-26 season due to a hamstring injury but was still productive when available, managing nine goals and two assists in his 27 league appearances last term.
He also scored two goals in Southampton’s run to the semi-finals of the FA Cup, including the opener in their quarter-final victory over Arsenal.
Stewart had stints with Ardeer Thistle and Kilwinning Rangers as a youngster before joining Albion Rovers in 2016.
The Irvine-born player then played for St Mirren, Alloa Athletic and Ross County – where he won the 2018-19 Scottish Championship and Scottish Challenge Cup – before joining Sunderland in 2021.
Stewart was prolific with the Black Cats, scoring 40 goals in 81 appearances to help the club win the EFL Trophy in 2021 and gain promotion to the Championship a year later.
His form at the Stadium of Light earned him a move to Southampton in 2023, where he score a total of 12 goals in 50 appearances.
“We are delighted that Ross has joined Swansea City, he brings a wealth of experience on and off the pitch,” said the Welsh club’s sporting director Ben Stevens.
“His performances last season in the Championship were a standout, and it earned him a deserved place in Scotland’s World Cup squad. We are very excited to see Ross in a Swansea shirt.”
Stewart becomes Swansea’s sixth permanent signing of the summer after Moussa Yeo, Elijah Just, Joseph Opoku, Stephen Welsh and Leo Walta, who had been on loan last season.
They have also signed Benfica left-back Tiago Parente on loan.
Valencia’s Andre Almeida and another midfielder, Randers’ Ousseynou Fall Seck, are also on the Swans’ list of targets.