The 20-year-old back-row forward, who was in the 24-man Wales squad that flew out to Australia on Tuesday for the World Cup, was short-listed for the 2017 Super League young player of the year award after a breakthrough season in which he played all but two of Saints' 32 games.
"Morgan has had an excellent year and his new contract is well deserved," St Helens coach Justin Holbrook said. "Since I joined the club, I have been impressed with his work-rate, ability to adapt and total commitment to his game and team-mates.
Thanks for all of the messages, really happy to extend my time @Saints1890 ðŸ”´âšªï¸ excited about the next few years ahead https://t.co/hYKnYSE3UZ
— Morgan Knowles (@knowlezy6) October 17, 2017
"His nomination for young player of the year was recognition of these attributes and I am really looking forward to watching him continue to develop over the next four seasons."
