The England midfielder has signed a five-year contract and joins for an undisclosed fee, believed to be around £10million.
The deal ends Rodwell's two injury-affected years at City, where he started just seven Premier League games after joining from Everton in a £12m move.
His prospects of first-team football at the Etihad were further hit when City signed midfielder Fernando from Porto earlier this summer.
Rodwell, who has three England caps, is Sunderland's fifth close-season signing and follows Jordi Gomez, Billy Jones, Patrick van Aanholt and former City team-mate Costel Pantilimon to Wearside.
@delusional? Just how obsessed are you? English players have had a huge premium on them for years. I thought everyone knew that? That's why Leeds went bust, £10+ million for the likes of Seth Johnson. Jesus Kevin Davies was once £7 million. Ask yourself why City will only have Hart or Chelsea Terry? It's because of these stupid rules, if you think it's working you are wrong. English football, the English national side have been gash for 40 years. Is that City's fault too? Or are City the only club doing anything about it? Remind me again where I can have a walk round the United campus...Your bitterness is so enjoyable!- charming_man