Dundalk have qualified for the Europa League group stage, and are one round away from the Champions League after beating Belarusian club BATE Borisov.
The Irish champions could be the first League of Ireland club to progress to the Champions League group stages.
Two David McMillan goals and a Robbie Benson strike earned the League of Ireland champions a 3-0 home-leg win, which ensured a 3-1 aggregate success.
McMillan scored either side of half time before Benson netted a late third.
Dundalk secure £5.9m Euro windfall
Dundalk were already guaranteed £1m after progressing to the Champions League third qualifying round but that has now increased to around £5.9m following Tuesday’s triumph.
The draw for the final Champions League qualifying round will take place in Monaco on Friday, and Dundalk could meet Scottish champions Celtic if they progress from their tie against Astana of Kazakhstan.
Other potential opponents include: Viktoria Plzen, Apoel Nicosia, Dinamo Zagreb, Ludogorets Razgrad, Olympiakos/Hapoel Be’er Sheva, Trencin/Legia Warsaw, Astra Giurgiu/FC Copenhagen or Partizan Tirana/Red Bull Salzburg.
The outstanding ties will be played on Wednesday.
Dundalk’s victory on Tuesday avenged last year’s 2-1 aggregate defeat by the Belarusians in the Champions League second qualifying round.
The League of Ireland champions secured their remarkable win despite having to move their home leg from Oriel Park to Tallaght Stadium in Dublin because of Uefa ground capacity rules.
BATE, regular qualifiers for the Champions League group stages, were left to rue missed first-half chances as Yuri Kendysh headed over and Aleksei Rios shot wide when well placed in the 16th minute.
Against the run of play, Dundalk took the lead on the stroke of half-time as Daryl Horgan’s cross picked out McMillan who guided a header past Sergei Veremko.
Dundalk had an escape in the 56th minute as Rios shot wide but three minutes later the Irish side were ahead in the tie as McMillan nodded a Dane Massey cross to the net.
After repelling some BATE pressure, Dundalk made the tie safe in the first minute of injury-time as substitute Benson broke clear and slotted past Veremko.
Match ends, Dundalk 3, BATE Borisov 0.
Second Half ends, Dundalk 3, BATE Borisov 0.
Substitution, Dundalk. Ciarán Kilduff replaces Daryl Horgan.
Goal! Dundalk 3, BATE Borisov 0. Robbie Benson (Dundalk) right footed shot from the centre of the box to the bottom left corner.
Igor Stasevich (BATE Borisov) is shown the yellow card for a bad foul.
Patrick Barrett (Dundalk) is shown the yellow card for a bad foul.
Vitali Rodionov (BATE Borisov) is shown the yellow card for a bad foul.
Substitution, BATE Borisov. Nikolai Signevich replaces Maksim Zhavnerchik.
Substitution, Dundalk. Robbie Benson replaces David McMillan.
Substitution, BATE Borisov. Mikhail Gordeychuk replaces Artur Pikk.
Goal! Dundalk 2, BATE Borisov 0. David McMillan (Dundalk) header from the centre of the box to the centre of the goal. Assisted by Dane Massey.
Second Half begins Dundalk 1, BATE Borisov 0.
Substitution, BATE Borisov. Aliaksandr Hleb replaces Aleksandr Karnitski.
First Half ends, Dundalk 1, BATE Borisov 0.
Goal! Dundalk 1, BATE Borisov 0. David McMillan (Dundalk) header from the centre of the box to the bottom right corner. Assisted by Daryl Horgan with a cross.
Substitution, Dundalk. Patrick McEleney replaces Ronan Finn because of an injury.
First Half begins.
Lineups are announced and players are warming up.