Ayoze Perez, Chancel Mbemba and the returning Dwight Gayle were on target for Rafa Benitez’s side, who rarely looked back after breaking the deadlock.
As comfortable an afternoon as it was for the Magpies, the crown looked to be heading to the South Coast after Glenn Murray’s second-half penalty for Brighton.
But, just seconds after Gayle added United’s third, word filtered through that Jack Grealish had netted for Villa at the death – sparking raucous scenes at St. James’ Park.
That said, there was little flow to the game early on, particularly where the Magpies were concerned. Isaac Hayden and DeAndre Yedlin both suffered knocks, with the former eventually forced to leave the field with a head injury.
Indeed, it was the visitors who looked the most purposeful, with Ryan Kent and Tom Bradshaw both sending efforts wide.
Slowly but surely, though, Newcastle began to get a foothold. 20 minutes in, Christian Atsu burst down the right and fed Perez just inside the area, whose shot was blocked by Callum Elder.
But, with their next attack, the Magpies took the lead. Atsu slid the ball into Yedlin’s path, and the American’s square was beautifully guided home by the in-form Perez.
Five minutes later, Atsu stung the palms of Adam Davies after cutting in from the flank.
The Ghanaian came close again before the interval, latching onto a neat Perez lay-off before forcing the Barnsley ‘keeper into a low stop.
Then, Massadio Haidara – a replacement for Hayden – cleared the target by some distance after meeting Perez’s driven cross at the back post.
Just moments into the second half, Perez was in again. The Tykes allowed a hopeful ball to roll from United’s half all the way into the Spaniard’s path, but Davies held firm.
With 55 minutes on the clock, a neat bit of footwork from Perez almost created an opening for Jack Colback, but the midfielder’s close-range effort was blocked by Davies.
Seconds later, Yoan Gouffran saw an 18-yard strike headed clear by Elder as Newcastle continued to dominate.
And, just before the hour-mark, their pressure told. After gathering Colback’s ball, Perez called Davies into action once more with a low-struck effort, and – though the ‘keeper was able to parry – the ball dropped perfectly for Mbemba eight yards out, who made no mistake.
Midway through the second half, the Barnsley stopper produced another fine save to deny Aleksandar Mitrovic, who met Jonjo Shelvey’s corner with a powerful header.
Shelvey himself then clipped the far post after an enterprising run – his last action of the afternoon.
His replacement, Mohamed Diame, quickly made his presence felt, drilling just wide of the far post from 18 yards.
With just over five minutes remaining, United’s Rob Elliot was forced into a save after a rare Barnsley attack, standing tall to deny Marley Watkins.
Elliot Lee – the son of former Newcastle midfielder Rob – then tried his luck from range, but the Magpies’ stopper managed to block.
It was United who had the final say, though, as Gayle – just minutes after coming on – ran onto Mitrovic’s header forward and coolly rolled the ball beyond Davies.
It was the final goal of a remarkable campaign, one which ended in suitably dramatic fashion. And, with the full-time score at Villa Park confirmed, the party started in earnest.
