The 19-year-old is an outside-back from Dewsbury and spent last season Down Under with the South Sydney Rabbitohs development team.
He has previously represented Yorkshire at Under-17s and England Community Lions, and joined Wakefield on a contract until the end of 2021.
Bruines later moved to Australia and was rewarded with a development contract with the South Sydney Rabbitohs while at the Coffs Harbour Comets.
St Helens head coach Paul Wellens said: “Wesley is a player with great potential, he has good knowledge of the game and the Super League competition.
“He has a really impressive work ethic and moving to Australia at a young age just shows how ambitious he is. But there’s a real resilience there as well from him. He’s really got his head down over the last few years and improved massively.
“This is a great opportunity for Wes, and having spoken with him I know it’s one he’s very eager to take. His addition gives our squad added depth and provides further competition for places.”
Bruines said: “The chance to be in the squad of the best team in England and the current champions is an opportunity I just couldn’t turn down. Once I had decided to come back home and there was interest there, I had to jump at it.
“I know how hard these opportunities are to come by. But I’ve worked for this my whole life. I think this is a step I’m ready for. And I’m ready to work even harder now for my new teammates and show the coaches what I’m all about.
“Having come home from Australia I can’t think of anywhere better to continue to improve and take that next step. I can’t wait to get started and push for a place in the squad.”
He will wear shirt number 34 for the 2023 season.