For all their endeavour in defence, Ireland struggled constantly to cope with the torrent of Spanish attacks as Torres proved he is back to his best with two clinically-taken goals.
Having decided the Euro 2008 final with the winning goal against Germany, Torres netted either side of David Silva second-half strike before his replacement Cesc Fabregas added the fourth seven minutes from time.
"That is a very good win for us," said Spain coach Vicente del Bosque.
"We brought in Torres to score goals, which is what he did and if we stay with this defensive line we will have things easy.
"It will be dangerous to play for the draw against Croatia and we won't play for the draw."
Ireland midfielder Keith Andrews admitted it had been a torrid night.
"We were chasing shadows," said Ireland midfielder Keith Andrews.
"We said before the match we should learn from our mistakes in the first game but then we shot ourselves in the foot by conceding an early goal. Make no mistake they are a top side and we were always up against it.
"In terms of the Italy game we are playing for pride simple as that."
With 66 percent ball possession, 26 shots on goal, 20 of which were on target, Ireland goalkeeper Shay Given had a busy night as Spain dominated while Ireland managed just six shots on goal in total.
The win puts Spain top of the group on goal difference and level on four points with second-placed Croatia, who Del Bosque's world champions face here at Arena Gdansk again on Monday.
Italy, who drew 1-1 with Croatia earlier, have two points in third and can still progress if they beat Ireland in Poznan, Poland, the same day, but the Azzurri are reliant on either Spain or Croatia winning in Gdansk.
Spain had complained to UEFA about the dry condition of the Gdansk pitch during Sunday's 1-1 draw with Italy as Fabregas labelled it "a disaster", but heavy rain during Thursday's match made the issue null and void.
Having used a 4-3-3 formation against Italy without a recognised striker, del Bosque elected to start Torres at the expense of Fabregas.
The Chelsea star rewarded the faith with the opening goal after just four minutes.
With Spain on the attack, Ireland defender Richard Dunne tackled Silva on the edge of the area, but Torres pounced on the loose ball and drilled his shot past Given from a tight angle.
Buoyed by the legions of green-clad fans, who clearly outnumbered the Spanish fans and sang until the end, Ireland battled forward, but any rare first-half forages into the Spain half were quickly snuffed out.
A heavy tackle on Andres Iniesta earned Ireland captain Robbie Keane the game's first booking on 36 minutes and Glenn Whelan followed just before the break for a foul on Silva as it finished 1-0 at the break.
Giovanni Trapattoni brought on Jon Walters for Simon Cox up front at half-time, but there was no stemming the tide of Spanish attacks.
A long-range shot from Iniesta was parried by Given, but fell into Silva's path, who jinked his way around defenders to roll his shot calmly past Given four minutes after the break.
After Given pulled off more heroics to deny Xavi Hernandez's corner shot, Ireland lifted their tempo with a series of attacks as Spain goalkeeper Iker Casillas was pressed into service.
The threatened third goal came when Silva released Torres, who raced away from Dunne and slotted home his shot on 70 minutes to give Given no chance before the Spaniard made way for Fabregas four minutes later.
The Barcelona star, who scored the equaliser against Italy, again showed his class as he drilled home his shot from a tight angle for Spain's fourth.