1860 Munich 0 - 1 Leeds United (Leeds win 3 -1 on aggregate)
Alan Smith fired his fourth goal of the season in Munich's Olympic Stadium to usher Leeds into the Champions League alongside Rangers, Manchester United and Arsenal.
The teenager, who scored twice against Everton on Saturday, grabbed the goal that could be worth up to £15million to Leeds a minute into the second half.
Mark Viduka won a tussle with Marco Kurz and when the ball fell for him, Smith displayed every ounce of his predatory instinct to bury the shot that could define Elland Road's season.
A full-strength Leeds side might have comfortably held off the Bundesliga's fifth-placed team but the makeshift content of O'Leary's emergency lineup meant their future was never secure until the end of an anxious second leg of their vital qualifier.
Leeds knew that no English team had succumbed to their opponents, who were eclipsed as Munich's premier side by neighbours Bayern in the 1970s and are only now re-asserting themselves in German football's upper echelon.
West Ham, Chelsea and Liverpool - who once walloped 1860 at Anfield by 8-0 - all proved too strong for Munich and Leeds had a powerful incentive to maintain tradition with the Champions League proper, not to mention that possible £15million in bonuses, awaiting last night's winners.
Leeds, having failed to reach that lucrative position in 1992 when Rangers won the so-called Battle of Britain, were already assured of avoiding champions Manchester United in the UEFA draw in Monaco.
More poignantly and with some relief, they are also certain, as prospective third seeds, to be drawn in different groups to fellow third seeds Galatasaray - their opponents when two fans were murdered earlier this year in Istanbul - and Besiktas, the other Turkish entrants.
There was a minimal presence in the section reserved for Leeds fans, reflecting perhaps their expectations of another expensive European run in the wake of last season's march to the UEFA Cup semi-finals. But Munich fans, drawn mainly from the city as opposed to Bayern's nationwide support, ensured a crowd approaching 50,000 - despite 1860's Bundesliga start of a scrambled draw and a lucky win either side of their 2-1 first-leg defeat at Elland Road.
They saw 1860 make their expected frenzied start against a team lacking key midfielders Eirik Bakke and Olivier Dacourt, both suspended after being sent off in the first leg.
But Nigel Martyn's goal was not put under a great deal of pressure, despite a hooked shot from danger-man Thomas Hassler that did not fly as close to Martyn's left-hand post as the crowd imagined.
In fact, it was Michael Hofmann's penalty area that came more under threat as Viduka got in a header from Ian Harte's cross, then Michael Duberry's surprise raid seemed briefly to have earned Leeds a penalty when he was dragged back by Daniel Bierofka. A linesman's offside flag indicated otherwise.
Still, Munich knew that Leeds were prepared to take the fight to them for the away goal that would make them favourites to go through and Smith - the thorn in Munich's side first time out - was in the thick of things once more.
He was spoken to quietly but firmly for a wild, high kick that referee Claus Bo Larsen thought put his opponents at risk but it was the 19-year-old striker who felt aggrieved after 21 minutes.
In tandem with Viduka up front, he looked poised to test Hofmann, only to be brought down from behind by Martin Stranzl in the penalty area.
Despite furious appeals, referee Larsen waved play on, prompting a touchline rant from O'Leary and the rest of the United bench.
United anger almost turned to joy within a minute when Viduka intercepted a poor back-pass from Borimirov but was denied the opener when his flick over the advancing Hofmann was blocked at point-blank range.
Viduka's next chance of glory came in 36 minutes as Bierofka made a desperate hash of his attempted clearance and presented the Australian with the ball on the edge of the area but the centre-forward, yet to score after his £6m move from Celtic, could only balloon his shot high over the crossbar.
A goal then would have steadied Leeds. Instead, the miss inspired Munich and Hassler almost slipped Agostino in for the opener but Martyn pulled off his best save of the first half from the former Bristol City striker.
Hassler, of course, was not finished, and with the last seconds of first-half stoppage time ebbing away he conjured a marvellous curling free-kick after Duberry fouled him, beating Martyn emphatically only for the ball to cannon back off the inside of the far post.
Danny Mills, who had stepped into defence to give a superb performance as one of O'Leary's fringe players, cleared off his line from striker Agostino after Martyn pulled off a great save from Borimirov as Munich tried to claw their way back.
But the best they could manage after that was a snap shot from Hassler that was drilled directly towards Martyn's safe hands.
1860 Munich
1860 Munich: (3-5-2): Hofmann; Stranzl, Kurz, Passlack (Winkler, 64min); Cerny, Borimirov (Beierle, 73), Hassler, Mykland, Bierofka (Tyce, 73); Agostino, Max.
Leeds United: (4-1-3-2): Martyn; Mills, Duberry, Woodgate, Harte; Radebe; Kelly, Jones (Evans, 73), Bowyer; Viduka, Smith.
Referee: Claus Bo Larsen (Den)