The disciplinary panel ruled Henson had intentionally struck Italy prop Alex Moreno with his elbow during last Sunday's European Cup match between the Ospreys and Leicester Tigers at the Liberty Stadium.
A second charge that he had then kicked Moreno was not upheld and that citing was dismissed.
The ban means Henson will miss the first three matches of Wales' defence of their Six Nations title.
Given Henson's lack of match practice this season because of injury it seems unlikely he will be ready to play in their match against Italy - which would be his first game after the ban comes to an end.
It rounds off a miserable second half of the year for Henson who struggled to command a place in the Test team during the Lions' tour of New Zealand this summer, and was cited after playing in only his second game of the current season after undergoing a groin operation in September.
Henson refused to speak after the hearing but a statement was read out on his behalf.
Derwyn Jones, the Ospreys team manager, said: "I will make a statement on behalf of Gavin Henson and Ian Evans, who won't be making a comment.
"Gavin Henson has received a 10-week ban whereas Ian Evans has received an eight-week ban from playing rugby.
"We are very disappointed with both verdicts and we will now consider our position as to whether or not to appeal the sanctions imposed."