Chelsea were crowned Premier League champions as Michy Batshuayi's late goal gave them the victory they required to secure the title at West Brom.
It looked as though Antonio Conte's side might be forced to delay their celebrations as they were frustrated for long periods by the resilience and organisation of their hosts.
But the mood changed and the title was won with eight minutes left as substitute Batshuayi, who had previously endured a season of struggle after his £33m move from Marseille, ended a scrappy passage of play by steering a finish high past Ben Foster.
The final whistle sparked wild celebrations among Chelsea's fans, and manager Conte was tossed high into the air by his squad.
The Italian can now set his sights on emulating compatriot Carlo Ancelotti's 2010 feat of winning the league and domestic Double as the Blues prepare for an FA Cup final against Arsenal at Wembley on 27 May.
Chelsea's celebrations were fully deserved - the culmination of a superb season's work by Conte and his squad.
They had to work hard for victory against a West Brom side that demonstrated all the qualities that have made this such a satisfactory season for them but, as so often, Chelsea got the job done.
The Blues' main attacking threats struggled to find a spark, with Eden Hazard's frustration summed up with one long-range shot that went out for a corner, but Conte's side found a way to win, illustrating once again why they are worthy champions.
The losses at home to Liverpool and at Arsenal in September that hinted at early struggles seemed an age away, as did the surprise defeat by struggling Crystal Palace at Stamford Bridge, and the setback at Manchester United.
Chelsea, even when not at their best, proved themselves the strongest and most complete side in the Premier League - and they proved it again on a night they were tested.
Conte's fingerprints are all over this title triumph - and his sure touch was on show again to fashion the victory they needed to get over the line with two games to spare.
The Italian knew his side needed a catalyst to break down West Brom, and it came with the introduction of Batshuayi and Willian for Hazard and Pedro with 15 minutes left.
Conte's masterstroke should have come as no surprise given the manner in which he has marshalled his forces, particularly the crucial switch to a three-man defence in September that turned Chelsea's season around and started a run of 13 straight league wins that led to the title.
No praise is too high for the 47-year-old, who took over a squad that looked broken after ending last season in 10th place and with the shadow of Jose Mourinho's sacking still hanging over the club.
This was his ultimate reward.
Batshuayi has been a misfit for much of this season, but whatever the future holds for the 23-year-old Belgian, he will always have a goal that won the title to his name.
Before this game, he had only figured only 24 times, played for 579 minutes and scored five goals - his sixth makes its mark in Chelsea history.
Chelsea still have two games to play in their title-winning season. They host Watford on Monday (20:00 BST) before receiving the trophy in their final game against relegated Sunderland at Stamford Bridge on Sunday, 21 May (15:00 BST). They then have the FA Cup final on 27 May.
West Brom travel to Manchester City on Tuesday, 16 May before finishing their season at Swansea the following Sunday (15:00 BST).