Welsby was born in Wigan, Lancashire. Playing for Shevington Sharks ARLFC as a child.
Playing career
Club career
In 2018, he made his Super League debut for St Helens against Hull FC.
He played in the club's 8-4 2020 Super League Grand Final victory over Wigan at the Kingston Communications Stadium in Hull. In the final seconds of play with the scores at 4-4, St Helens attempted a field goal which rebounded off the goal post. Welsby was the first player to the ball from the ricochet and he scored after the full-time siren to win the match for St Helens.[3][4]
In round 20 of the 2022 Betfred Super League season, Welsby kicked a drop goal in golden point extra-time to win the match for St Helens 13–12 against bottom placed Wakefield Trinity. In September, Welsby was awarded young player of the year at the 2022 Super League awards ceremony.[8]
On 24 September, Welsby provided two try assists in St Helens 24-12 Grand Final victory over Leeds.[9]
In the 2023 World Club Challenge, Welsby scored the opening try for St Helens in their 13–12 upset victory over Penrith.[10]
In round 15 of the 2023 Super League season, Welsby made his 100th appearance for St Helens and scored two tries in the clubs 34–16 victory over rivals Wigan.[11]
In round 20 of the 2023 Super League season, Welsby scored two tries for St Helens in their 22–18 victory over Leeds.[12]
Welsby played 29 games for St Helens in the 2023 Super League season scoring 11 tries as the club finished third on the table. Welsby played in St Helens narrow loss against the Catalans Dragons in the semi-final which ended St Helens four-year dominance of the competition.[13]
On 20 December 2023, Welsby signed a four-year contract extension to remain at St Helens until the end of the 2027 Super League season.[14]
Welsby played 23 matches for St Helens in the 2024 Super League season including their golden point elimination playoff final loss against Warrington.[15]
International career
On 15 October 2022, Welsby made his England debut against Samoa in the 2021 Rugby League World Cup scoring one try and providing two assists as England won the match 60–6.[16]
Welsby played in all five matches for England at the tournament including the semi-final where he made a crucial handling error in golden point extra-time against Samoa. England would go on to lose the match 27–26 at the Emirates Stadium.[17]
In the absence of regular captain George Williams through suspension, Welsby was named captain for the first Tonga test on 22 October 2023, becoming the youngest ever captain.[18]
Welsby played in all three tests as England won the series 3–0.[19]