The Andalusian club were trailing 3-2 on aggregate in their semi-final tie against La Liga rivals Valencia when Mbia leaped to nod the ball into the net and set up a showdown with Portuguese side Benfica in Turin on May 14.
Mbia, who is on loan in Seville from Championship side Queens Park Rangers, collapsed to the ground and was engulfed by his team-mates as the Valencia players and their fans packed into the Mestalla were left shell-shocked.
"I feel very happy because the tie was looking very difficult," Mbia said in a pitch-side interview with Spanish television.
"The goal was incredible," added the 27-year-old former Marseille player.
"This goal is for my family, for my father and for my mother. I am very emotional.
"It is the happiest moment of my life. It was important to go to Turin after working so hard."
Sevilla are looking to repeat their successes in Europe's second-tier club competition from 2006 and 2007 when it was known as the UEFA Cup.
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