Tim Cahill booked Millwall an FA Cup Final clash with Manchester United and a place in next season's UEFA Cup with a first-half match-winner against Mick McCarthy's Sunderland at Old Trafford.
Cahill hit his third goal of Millwall's remarkable cup run to cap a memorable week for the midfielder, who made his debut for Australia in midweek after a nine-year battle over his eligibility.
On 26 minutes George McCartney's pass back to Phil Babb was weak and Paul Ifill intercepted and raced into the area. His shot was blocked by Mart Poom but Cahill's rebound found the net with the help of a deflection off McCartney.
Cahill was at the heart of everything good about Millwall, and it was his right-wing cross from a fast break that almost provided a second for the Londoners in the 74th minutes.
Any chance Sunderland had of a comeback disappeared when Jason McAteer was sent off for a second yellow card with four minutes remaining.
Jubilant Millwall player-manager Dennis Wise said: "It's fantastic. They've worked extremely hard. They are a great bunch of lads and I'm proud of all of them. I've told them all along 'if you believe in yourselves you'll go far' and they deserve it."
Sunderland boss Mick McCarthy felt his side had every reason to be proud of themselves despite having lost.
"You always feel hard done by when you are not in the final," reflected the former Republic of Ireland manager. "We played well and could not have done any more except score. I am proud of the lads, but devastated for them."
McCarthy added: "We started really well but goals change games and they upped the tempo after theirs. They took it to us and were better then.In the second alf we played as well as we can, but we did not get the break and did not get the goal."
Filed by Barry J Whyte