Mohamed Bayo headed a 98th-minute winner as Guinea reached the quarter-finals of the Africa Cup of Nations with victory over 10-man Equatorial Guinea, who had earlier missed a penalty.
Equatorial Guinea midfielder Federico Bikoro was dismissed 10 minutes after the break for catching Bayo in the ribs with his studs.
The National Thunder were awarded a spot-kick midway through the second half after Sekou Sylla caught Iban Salvador, but captain Emilio Nsue hit the base of the right-hand upright.
And, with the game set to head to extra time, striker Bayo stooped to guide Ibrahim Diakite's cross from the right flank just inside the near post in the final minute of added time.
The West Africans will face either Egypt or DR Congo in the last eight in Abidjan on Friday, and will find out the identity of their opponents when those sides meet later on Sunday (20:00 GMT).
Guinea had barely made their one-man advantage count in the final 35 minutes, although goalkeeper Jesus Owono was forced to tip a header from striker Serhou Guirassy over the bar in the closing stages.
Yet Bayo's dramatic late goal broke the resistance of the Equatoguineans and sent Syli National into the last eight for the first time since 2015, as Guinea triumphed for the first time in seven appearances in the knock-out stages at the finals.
Nsue unable to continue National Thunder run
Equatorial Guinea had been the surprise package from the group stage, winning Group A ahead of Nigeria and hosts Ivory Coast as Nsue netted five goals to top the scoring charts.
The first half saw scant action in the final third, with Bayo sending an effort into the side-netting early on and Guinea team-mate Morgan Guilavogli firing over from long range.
Nsue blasted a volley over the bar from 12 yards two minutes after the restart, but the complexion of the game changed when Bikoro was shown a straight red after following through with a clearance in midfield and catching Bayo with some force.
Equatorial Guinea were handed a glorious chance to take the lead when the Video Assistant Referee intervened to send Omar Artan to his screen on the touchline, and the referee decided Sylla had caught Iban Salvador on the back of the leg after the midfielder had controlled a pass and awarded a penalty.
But veteran striker Nsue, who plays in the third tier in Spain, could not add to his tally at the finals despite sending Guinea keeper Ibrahim Kone the wrong way.
Aside from substitute Guirassy's header, a tame effort from right-back Diakite was all Guinea could muster before the board for eight minutes of added time went up and Bayo won it at the death.
Equatorial Guinea had reached at least the quarter-finals on their previous three appearances at Afcon, but Juan Micha's side could not repeat that achievement as 34-year-old Nsue was left to rue his costly miss while Guinea celebrated at the final whistle.
The West Africans, managed by one-time Arsenal striker Kaba Diawara, had finished behind holders Senegal and Cameroon but progressed to the knock-out stages as one of four best-ranked third-placed sides.
Line-ups
Equatorial Guinea
Formation4-4-1-1
1Owono
15Akapo21Orozco16Coco11Ndong
6Salvador4Bikoro22Ganet8Buyla
7Machín
10Nsue
1Owono
15Akapo
21Orozco
16Coco
11Ndong
6Salvador
4BikoroBooked at 55mins
22Ganet
8BuylaSubstituted forAsuéat85'minutes
7Machín
10Nsue
Substitutes
2Senra
3Anieboh
5Elo
12Ondo
13Embela
14Balboa
18Ela
19Asué
20Eneme
23Sapunga
26Nabil
27Siafá
Guinea
Formation4-4-2
22Koné
12Diakité5Diakhaby17Jeanvier3Sylla
7Guilavogui20Konaté6Diawara21Sylla
11Bayo18Camara
22Koné
12Diakité
5Diakhaby
17JeanvierBooked at 41mins
3Sylla
7GuilavoguiSubstituted forGuirassyat60'minutes
20KonatéSubstituted forKeïtaat79'minutes
6Diawara
21SyllaSubstituted forKamanoat79'minutes
11Bayo
18Camara
Substitutes
1Keita
2Conté
4Sow
8Keïta
9Guirassy
13Camara
14Cissé
15Cissé
16Camara
19Kamano
24Kanté
Referee:
Omar Artan
Match Stats
Live Text
Match ends, Equatorial Guinea 0, Guinea 1.
Second Half ends, Equatorial Guinea 0, Guinea 1.
Goal! Equatorial Guinea 0, Guinea 1. Mohamed Bayo (Guinea) header from the centre of the box to the bottom right corner. Assisted by Ibrahim Diakité with a cross.
Foul by José Machín (Equatorial Guinea).
Ibrahim Diakité (Guinea) wins a free kick on the right wing.
Iban Salvador (Equatorial Guinea) wins a free kick in the defensive half.
Foul by Issiaga Sylla (Guinea).
Emilio Nsue (Equatorial Guinea) wins a free kick on the left wing.
Foul by Mouctar Diakhaby (Guinea).
Basilio Ndong (Equatorial Guinea) wins a free kick in the defensive half.
Foul by Aguibou Camara (Guinea).
Attempt saved. Serhou Guirassy (Guinea) right footed shot from the left side of the box is saved in the centre of the goal. Assisted by Aguibou Camara.
Delay over. They are ready to continue.
Delay in match because of an injury Ibrahim Diakité (Guinea).
Attempt saved. Ibrahim Diakité (Guinea) right footed shot from the right side of the box is saved in the bottom right corner. Assisted by Julian Jeanvier.
Attempt missed. Serhou Guirassy (Guinea) right footed shot from the centre of the box is too high. Assisted by Aguibou Camara with a cross following a corner.
Corner, Guinea. Conceded by Jesús Owono.
Attempt saved. Serhou Guirassy (Guinea) header from the centre of the box is saved in the top left corner. Assisted by Aguibou Camara with a cross.
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