Dani Ceballos stepped up to be the hero as the Real Madrid loanee scored in stoppage time to send Arsenal into the FA Cup semi-finals.
Mikel Arteta's side looked to have been frustrated when David McGoldrick levelled the score at Bramall Lane in the 88th minute with a volley from close range to cancel out Nicolas Pepe's first-half penalty.
But Arsenal were not to be deterred and following a swift counter-attack, Ceballos drilled low and hard through Dean Henderson with the clock ticking down to avoid extra time and ensure Arsenal joined Manchester United in reaching the FA Cup final four.