Tim Cahill savoured his history-making goal for Millwall who reached their first ever FA Cup final.
The Lions, who last made the semis in 1937, defeated Sunderland at Old Trafford in a cup clash involving two teams from the first division.
And it was a special moment for Cahill, Millwall's Australian midfield player as his goal earned a final against Manchester United.
Cahill said: "Manchester United were my boyhood heroes, and hopefully we'll be able to do a job against them.
"Hopefully we have gained a lot of respect from this Cup run. As for my goal it was about being in the right place at the right time." And Millwall striker Neil Harris could not believe his side had made it to the Millennium Stadium.
He explained: "We have never got anywhere before, but we have got to the final quietly.
"Manchester United are English football. They are a massive club, but they have lost a few games against bottom sides and we will give it our best shot.
"It is frightening and when we pick up the papers tomorrow maybe it will have sunk in." Millwall had an early let off when John Oster's free-kick struck the underside of the crossbar, but bounced to safety.
Cahill struck the decisive goal in the 26th minute after a dreadful defensive mix up between George McCartney and Phil Babb.
Paul Ifill broke clear but was brilliantly denied by goalkeeper Mart Poom only for the rebound to fall to Cahill who struck a shot into the roof of the net.
Millwall paid a heavy price for their first-half lead with Ifill and Kevin Muscat both taken from the field on stretchers, though Muscat later hobbled back to the dressing room.
Sunderland made a splendid start to the second half with Paul Thirlwell, Kevin Kyle and Julio Arca having excellent chances in the opening ten minutes, but they could not find a way past goalkeeper Andy Marshall.
Millwall might have doubled their lead in the 74th minute following a break away when Cahill crossed from the right for Danny Dichio whose free header was superbly blocked by Poom.
Sunderland, who had Jason McAteer sent off in the 86th minute for a second booking, staged a grandstand finish with McCartney firing wide when he ought to have hit the target while in the dying seconds substitute Matt Piper forced a great save from Marshall.