The 21-year-old, born in Bulawayo, stands 6ft 5in tall and weighs 17st 9lbs and can operate in the second row or back row.
Williams, who has enjoyed an outstanding 2013 Varsity Cup campaign - winning man of the match in the semi-final against UJ - will move to England his summer on a two-year deal.
Head Coach Richard Hill described Williams as a massive prospect for Warriors who would add yet more power to the pack at Sixways.
"Mike is primarily a lock who has the ability to play at six and is a young player who excites us," said Hill. "He reminds me in many ways of Joe Launchbury and he is a talent for us to work with.
"He is an athletic and big man who is also English qualified and was keen to make an impression in this country when he came to visit us earlier this month.
"Mike has been part of a strong rugby set-up in South Africa and has real potential to get even better as part of the Warriors."
Williams joins Ignacio Mieres, Leonardo Senatore, Agustin Creevy, Paul Warwick, Paul Andrew and Ofa Fainga'anuku in agreeing moves to Sixways this summer.
Watch the new Warrior in action - click HERE to see Mike Williams.
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