The highly-rated 19-year-old is a product of the club's academy and has been a regular for the Warriors during the 2014 campaign.
"He is a very talented young player who shows great desire to be the best," coach Shaun Wane told the club website.
"Make no mistake, we are the envy of many Super League clubs in getting George's signature."
Williams added: "I thoroughly enjoy the environment here and intend to repay the trust in me by working hard, continuing to improve and play my role in helping this team to achieve great things."
Wigan half-back George Williams has agreed a new four-year contract with the reigning Super League champions.