The 25-year-old was cited in the wake of Saturday's 22-18 Champions Cup defeat at Racing 92 and pleaded guilty at an independent disciplinary committee hearing on Wednesday.
A statement issued by European Professional Club Rugby said: "The Leicester Tigers flanker, Mike Williams, has been suspended for one week following an independent Disciplinary Hearing in London today arising from his club's Champions Cup, Round 1 match against Racing 92 at Stade Yves-du-Manoir.
"Williams was cited by match Citing Commissioner, Stefano Marrama (Italy), for charging into a ruck and making contact with the head/face area of the Racing 92 centre, Henry Chavancy, in contravention of Law 10.4 (h)."
Williams will miss Saturday's home clash with Castres as a result of his suspension after the committee ruled that he should have received a red card, although the initial penalty was halved as a result of his guilty plea and apology.
The statement continued: "The committee upheld the citing complaint and determined that the offence had warranted a red card. The committee found that the offence was at the low end of World Rugby's sanctions and selected two weeks as the appropriate entry point.
"The committee reduced the sanction by one week due to the player's guilty plea, expression of remorse and immediate apology before imposing a suspension of one week.
"Williams is free to play on Monday, 23 October, and both the player and EPCR have the right to appeal the decision."
Tigers head coach Matt O'Connor had earlier expressed his misgivings over Williams' citing.
He said: "I think there's 50 or 60 of those in a game. I think we're in a really dangerous place if that's going to be the standard of what we're looking at in relation to bringing blokes before the judiciary.
"There's no malice in it, there's no genuine intent to harm or injure, it happens 60 times a game."
Related links
