Mark Percival has committed his future to St Helens until the end of the 2024 Super League season.
The England centre, who joined Saints as a 14-year-old, has scored 88 tries and kicked 225 points in 158 appearances.
Percival, who made his first-team debut against Leeds Rhinos in 2013, was among the try scorers as Saints defeated Salford Red Devils to win the Grand Final last season.
"I am over the moon. I have loved being at this club since I joined at the age of 14," Percival, who scored 12 tries in 26 appearances last season, told Saints' official website.
"Leaving has never really come into my mind and to be offered a five-year deal, I am buzzing."
Percival, who also won the 2014 Grand Final with Saints, is set to miss the next few weeks having injured his shoulder and sternum in the 19-0 loss to Warrington Wolves last time out.
Head coach Kristian Woolf added: "I'm delighted Mark has signed a new deal with us. He's as tough as they come and although only in his mid-twenties, is a player with a vast amount of experience.
"Having won two Grand Finals he clearly knows how to win and that is hugely beneficial to our group and the younger players.
"We will miss Percy over the coming weeks given his injury, but when he is back fit, I have no doubt he will continue to be an important player for us over the coming years."