The game looked to be headed for extra-time and penalties when in the 89th minute Alex Berenguer stepped up to score the decisive goal, sending his team through and Madrid home.
The result is sweet revenge for Athletic, who suffered a chastening 2-0 defeat to Madrid last month in the final of the Supercopa de Espana in Saudi Arabia.
They can now look forward to facing either Rayo Vallecano, Valencia or Real Betis in the semi-final of the Copa depending on what hand the draw deals them.
The result is a real shock given Madrid are currently four points clear of second-placed Sevilla at the top of La Liga and Athletic are down in tenth. But Marcelino’s men can beat anybody and they proved it in Bilbao tonight.
FINAL I ¡¡𝗟𝗢 𝗟𝗢𝗚𝗥𝗔𝗠𝗢𝗦!!
— Athletic Club (@AthleticClub) February 3, 2022