Steven Davis scored twice as Southampton came from behind to beat second-placed Tottenham.
Home forward Son Heung-min chased a lost cause for the opener, gliding past Fraser Forster and coolly tucking the ball into an open net.
The visitors equalised through Davis, who slotted in under Hugo Lloris following Dusan Tadic’s cut-back.
Spurs’s Jan Vertonghen had a header cleared off the line, before midfielder Davis stroked in the winner.
Substitute Nacer Chadli could have saved a point for the hosts deep in stoppage time, but his poked effort was kept out by the big frame of Forster.
Having challenged for the Premier League title for most of the season, Tottenham now lie 10 points adrift of champions Leicester and are hanging on to second spot, three points ahead of local rivals Arsenal.
History repeating itself for Spurs
Manager Mauricio Pochettino has been praised this season for instilling in Tottenham a steeliness they had lacked in the past.
Nevertheless, having been the Foxes’ closest challengers they have come up short, and dropping 20 points from winning positions – the most in the division – has clearly played a big part.
Arsene Wenger’s Arsenal now have a chance to overtake Spurs and continue a run that has seen them finish above their north London rivals every season since 1995 – having missed out on the title, it would be a further, bitter blow.
The hosts did take the lead through South Korean Min’s calm finish, but could not find a way past England international Forster thereafter.
The big goalkeeper got down quickly to save Christian Eriksen’s effort in the first half and made a sharp stop off top scorer Harry Kane, who remains on 25 for the season.