Manchester United's eight-match winning streak came to an abrupt end at Ewood Park as Garry Flitcroft's 40th minute strike was enough to send the visitors packing.
Blackburn captain Flitcroft kept his cool following a Damien Duff free-kick to hammer a low half-volley past Fabien Barthez and seal a deserved three points for his team.
United will point to missed chances in the first half as the reason for the defeat but despite the second-half introduction of Roy Keane and David Beckham, they failed to hit the heights of recent weeks.
Juan Veron was unavailable so Diego Forlan started and both he and Ruud van Nistelrooy missed golden opportunities as the away team started confidently.
Rovers grew in stature as the game progressed, a drive from David Dunn forcing Barthez to tip over in the 37th minute.
Four minutes later, Blackburn did take the lead, Flitcroft being in the right place at the right time to score.
Ole Gunnar Solskjaer made Brad Friedel work with a low shot seconds before the interval but the balance in the game had most definitely changed.
Blackburn could have had more goals in the second period, ex-United front pairing Andy Cole and Dwight Yorke causing lots of problems for Wes Brown and Mikael Silvestre.
However, shortly after Keane made his entrance, United should have equalised when Paul Scholes sent van Nistelrooy clear. The formidable presence of Friedel distracted the striker and he could only fire into the sidenetting.
Even with Beckham brought on by the visitors with 20 minutes left, Blackburn more than held out. In fact, Yorke should have scored with three minutes to go, racing on to a Cole pass, but hitting his shot into the crowd.
Rovers boss Graeme Souness was understandably delighted with both the result and the impressive performance from his team: "I'm very pleased, they are a top team and I thought we did very well against them." These two sides are due to meet again twice next month in the Worthington Cup semi-finals.