Llanelli Scarlets were crowned Celtic League champions as Wales star Stephen Jones produced a virtuoso farewell performance to deny Ulster at Stradey Park.
Fly-half Jones, who will join French club Montferrand this summer, kicked 18 points and created a brilliant try for centre Matthew Watkins.
He was the one Scarlets player that Ulster could not handle on a night of raw emotion when Llanelli became Wales' first Celtic title winners.
Jones finished with five penalties and a drop-goal, although it was the magical outside break which created Watkins' try that will long live in the memories of Scarlets supporters.
The teams were separated by just one point before kick-off, giving league organisers a dream finale to this season's competition.
The visitors were ahead inside four minutes, courtesy of a 50-metre penalty from David Humphreys, and it took Llanelli a time to settle, especially with the stakes so high.
Jones settled their nerves by stroking over a 14th-minute penalty, yet there was little between the sides during an intense opening quarter.
Humphreys regained the initiative for Ulster through his second successful strike - he missed a short-range effort just four minutes earlier - but Jones was well wide when
Llanelli had a penalty chance following lock Matt Mustchin's body-check on wing Garan Evans.
Jones was at the heart of Llanelli's best moments, and a penalty just before half-time edged his team ahead.
Humphreys' second long-range penalty tied things up at half-time, yet Ulster should have been ahead following another uncharacteristic Humphreys miss after Mustchin was tipped out of a lineout.
Llanelli had the second half's first scoring chance when flanker Simon Easterby charged down a Humphreys kick and Jones moved to within sight of Ulster's line.
Ulster then infringed during a spell of frantic defending, allowing Jones to complete his penalty hat-trick, which gave the Scarlets fresh heart.
And Jones then showed his ability as an attacker, slicing open Ulster's midfield defence in scintillating fashion to send Watkins over for a try that sent Stradey Park wild.
Jones quickly booted his fourth penalty, while full-back Barry Davies had a try disallowed following a marginal forward pass as Ulster's challenge started to slip off the rails.
Another Jones strike sealed the deal, offering no way back for Ulster, before a night of prolonged celebration could begin in earnest, despite Neil McMillan's late consolation try,
converted by Humphreys.
The RBS 6 Nations Championship 2015 was not poised to go down as one of the more "vintage" Championships, though there was great anticipation as the action headed into its final day. What transpired was something that nobody could foresee: "The Greatest Day in Rugby's Greatest Championship."