The England international has been at Sandy Park since 2015 and the tight-head has played in just short of 100 games, scoring 10 tries.
Williams joined the Chiefs from Championship side Jersey Reds and was a member of the club’s title-winning side in 2017.
“It was an easy decision to make,” Williams told the club’s website. “I’ve been here five years now and I’m very happy down here. Ever since I came to the club it’s been awesome and I’ve loved pretty much every minute of it.
“I knew when I left Jersey that I was moving to an ambitious club who would bring the best out of me and challenge me in a testing environment. That’s been the case from day one, but I still feel there is more to come from me.”
Williams, who has won 18 caps for England, feels Exeter can only go from strength to strength.
“I think for everyone at the club, we’re not happy sitting on our laurels and just accepting that we’re going to do this and that,” added Williams.
“As a professional, you always feel you can kick on and get more out of yourselves. Here at Exeter, everything is laid out for us and the club give us a great foundation from which to build.”
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