Dele Alli scored twice as Tottenham came from behind to earn a first win at Stamford Bridge in 28 years and damage Chelsea's hopes of finishing in the Premier League top four.
A win would have moved the Blues to within two points of fourth-placed Tottenham and, after soaking up some Spurs pressure, they took the lead when Alvaro Morata headed in Victor Moses' cross.
But Tottenham levelled just before the break, as Christian Eriksen hit a fierce, dipping effort from 25 yards that dropped just under the bar and over a stranded Willy Caballero.
Alli then took centre stage in the second half, putting Tottenham ahead just after the hour mark when he produced a sublime first touch to bring Eric Dier's ball under control before slotting beyond Caballero.
The England midfielder was then well-placed to stab in following a goalmouth scramble after a good run by Son Heung-min.
Victory for Tottenham means they moved eight points clear of Chelsea in fifth with seven games remaining.