Winger Hammill, 25, who spent four months on loan with the Terriers last season, has signed a three-year deal after Huddersfield agreed an undisclosed fee with Wolves.
"I know just how much of an impact Adam can have at Championship level and I understand he showed glimpses of that during his loan spell here last season before I arrived," Robins told the club's official website.
"Our job - and the challenge for Adam - is to work very hard on the training pitch and get him playing at a consistently high level, because if we can we have a very exciting player on our hands.
"Adam has lots of ability with the ball at his feet and will fit very well into the style of football we want to play, as he can play on either side or with the main striker."
Hammill, who began his career at Liverpool, spent 18 months at Barnsley before Wolves paid £500,000 for him in January 2011.
But he failed to settle at Molineux and had a loan spell at Middlesbrough during the second half of the 2011/12 season and made 16 appearances for Huddersfield while on loan up until January this year.