Soliola has scored over 20 tries for Sydney Roosters
St Helens have agreed a deal to sign New Zealand international Sia Soliola on a three-year contract from 2010.
The 22-year-old centre currently plays for Sydney Roosters and has made more than 80 appearances for them since his NRL debut in 2004.
"I am really looking forward to playing in England next year as St Helens is a fantastic club," said Soliola.
"I will be linking with my former Roosters team-mate Chris Flannery as well as Test team-mate Tony Puletua."
Soliola continued: "Going to England is something that has appealed to me now for a while.
"I will get the opportunity to play in a world-class team and, at the same time, experience life in a different country."
While Soliola is excited at the prospect of running out at Knowsley Road, he was keen to pay tribute to the club he will leave behind next season.
Sia Soliola will be an exciting addition to St Helens and to Super League next season. He is already one of the best centres in the game and at 22, has his best years ahead of him
St Helens chairman Eamonn McManus
"The Sydney Roosters have been fantastic to me since I came over here as a teenager. I doubt I could play for any other club in Australia - hence my decision to experience something different going forward," he said.
St Helens coach Mick Potter is delighted with the capture of the Kiwi and believes Soliola can add an extra dimension to his side next season.
"Sia will add size, speed and athleticism to our backline and will be a great addition to our squad next year."
Saints chairman Eamonn McManus believes the club have completed a shrewd piece of business with the signing of Soliola.
He said: "Sia Soliola will be an exciting addition to St Helens and to Super League next season. He is already one of the best centres in the game and at 22, has his best years ahead of him."