Young had a fine game in front of the watching Fabio Capello
Ashley Young and John Carew both scored twice as Aston Villa outclassed Birmingham, keeping their local rivals deep in relegation trouble.
Young's rasping shot gave Villa the lead and Carew nodded home the winger's free-kick shortly before the break.
Carew tapped in from close range for Villa's third and Young beat two players before scoring his second goal.
Mikael Forsell scored a consolation for Birmingham, but there was still time
for Gabriel Agbonlahor to grab a fifth.
Europe is 'tantalisingly close' - O'Neill
Villa have now scored 15 goals in their last three Premier League games as they keep the pressure on Everton - who they meet next Sunday - for a Uefa Cup place.
Birmingham enjoyed a decent spell of possession early on, culminating in an effort at goal from David Murphy, but the visitors failed to really test Villa keeper Scott Carson.
The home side soon began to stamp their authority on the game as they over-ran Birmingham in midfield, with Carew going close with a header from an inswinging corner and the influential Gareth Barry firing narrowly wide with a snap-shot from inside the area.
Birmingham, with in-form striker Mauro Zarate desperately short of service up front, were almost non-existent as an attacking force, and Villa had the next chance - Barry's free-kick drawing a reasonable save from Maik Taylor.
Stiliyan Petrov's swirling effort caused problems for the Blues keeper, and the dam finally burst when Olof Mellberg's mishit pass bounced into Young's path.
With England coach Fabio Capello among the 42,640 sell-out crowd, Young did his international prospects the power of good as he unleashed a fantastic effort past Taylor and into the bottom corner.
There was a hint of controversy in the build-up though, with referee Mark Clattenburg breaking up a confrontation between Young and Mehdi Nafti with a full-blooded shove to the Birmingham defender's chest as play went on.
Undoubtedly fired up by the unexpected intervention, Nafti beat two players in a narrow space moments later before firing over for the Blues.
But it was not long before Villa surged further ahead, as Young's accurate free-kick found an unmarked Carew inside the six-yard box, allowing the big striker to nod home from point-blank range.
McLeish admitted it was a 'bruising' defeat
It was more of the same after the break, with Birmingham's defensive frailties ruthlessly exposed by a rampant Villa.
Young was involved again as his long ball found Barry - coming back from a borderline offside position - and the England midfielder unselfishly squared for Carew to guide the ball into an empty net.
With the match effectively over as a contest, Young scored his second on 63 minutes, beating two players before firing a low shot towards goal.
Taylor saved the initial effort but the ball bounced perfectly into the 22-year-old's path and he slotted home to cap an excellent individual display.
With his team's fans pouring out of the ground by the minute, Blues substitute Forssell - on for Zarate, who had a mini-tantrum as he left the pitch - cut the gap after a good passing move.
But the final goal went the home side's way after a howler from ex-Villa defender Liam Ridgwell allowed Agbonlahor to race through the middle and slide the ball into the centre of the goal.
It sealed his side's biggest derby win since 1988 - and kept Birmingham in the bottom three of the table.
• Aston Villa boss Martin O'Neill:
"Winning was the most important thing, but to win so convincingly is a great boost for us.
"I thought we played brilliantly. We are a really decent side going forward.
"Ashley Young and John Carew were both absolutely outstanding. Ashley couldn't have done any more in front of Fabio Capello.
"We're still there fighting for the Uefa Cup. We're in full flow and the Everton game (on 27 April) is a massive one for us."
• Birmingham boss Alex McLeish:
"We were on the end of a bruising from a really good Villa side.
"Villa's front men were on fire and we were unable to string any passes together until the second half.
"You have to say that Villa's agenda is totally different to ours - the bottom line is that they are a better team.
"It's all about our next three games - we have to take as many points from those games as we can. This match doesn't mean we're going down
"I can take some things from the game and we have been a different team at home."
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