Holt has agreed a three-year contract at the DW Stadium and he becomes the seventh signing since Owen Coyle took over as manager.
Coyle is delighted to have added the 32-year-old to his squad following the sale of striker Arouna Kone to Everton earlier in the day.
"This is a fantastic piece of business for us at a really good price," Coyle told the club's official website.
"Grant is a proven goalscorer at every level and he will definitely bring something new to the table that we were missing in the squad.
"There is already a great buzz about the place since the new boys have started coming through the door and this is another one that will really lift the place.
"He's been a hero to the fans at every club he's been and I know the Norwich fans are sad to see him go, he's been one of the icons of their success in recent years. But now it's the Wigan fans' turn to enjoy him and we're all delighted he's coming on board."
Norwich boss Chris Hughton added: "Grant was an important part of what we managed to achieve in the Barclays Premier League last season.
"Of course before I came to the club I was very aware of the magnificent job he had already done in the three years prior to that as well.
"When we look back I'm sure we will all agree that to score the amount of goals he has done for the club in that time is a remarkable achievement.
"Myself and all of the staff certainly wish him all the best for his time at Wigan."
Holt netted 15 league goals in Norwich's first season back in the top flight in 2011/12, but he only scored eight Premier League goals last term and City manager Chris Hughton has been actively seeking reinforcements up front.
He joined Norwich in 2009 and has also played for the likes of Rochdale, Nottingham Forest, Blackpool and Shrewsbury after starting his career at non-league Workington.
The hard-working forward joins Marc-Antoine Fortune in boosting Wigan's attacking options, while Coyle has also signed Scott Carson, Thomas Rogne, Stephen Crainey, James Perch and Chris McCann since replacing Roberto Martinez as manager.