Albion lose on Astle Day - Report and pictures
Jamie Vardy's stoppage-time winner sent Albion to a crushing defeat to give a flat end to Jeff Astle Day at the Hawthorns.
A sell-out crowd paid an emotional tribute to Jeff Astle before and during the game.
But their team, wearing replica 1968 FA Cup final kit, responded with a dismal display and were lucky to be level before Vardy struck the winner in the first minute of added time.
Albion had twice led through Darren Fletcher and Craig Gardner, but David Nugent and Robert Huth levelled for the Foxes before they snatched all three points late on.
It leaves the Baggies still looking nervously at the Premier League relegation zone with a desperately hard run-in to come.
The crowd played a part in a day of tributes to Astle, including placards in the Birmingham Road End that spelled out 'Astle, King' in the ninth minute.
There was a 1968 pre-match soundtrack and many fans also donned retro kit.
Albion should have led in the fifth minute when a free-kick from the right by Gardner found the head of Joleon Lescott, whose close-range glancing effort flew over.
But it was another set-piece three minutes later that brought the opening goal.
A right-wing corner from Chris Brunt was glanced towards goal by Fletcher with Hawkeye awarding the goal despite Estaban Cambiasso's desperate attempts to hook it away.
Replays showed the ball had clearly crossed the line.
Kasper Schmeichel in the Leicester goal made a comfortable save from Saido Berahino on 18 minutes but, two minutes later, the Foxes were level thanks to some awful Baggies defending.
Leonardo Ulloa beat Gareth McAuley to flick on a hopeful long ball and Nugent nipped in behind Joleon Lescott to score.
Nugent dragged a shot wide on 24 minutes as the home side became ragged. But on 26 minutes the Baggies restored their lead.
There was a hint of controversy with Leicester fans claiming the ball had crossed the touchline for a throw-in during the build-up, although replays suggested James Morrison had just kept it in.
From there, Brunt delivered a fantastic cross that struck the head of Brown Ideye and fell for Gardner to volley home with the aid of a deflection off Wes Morgan.
The remainder of the first half was scrappy but Leicester should have drawn level just before half-time as Albion gifted them another chance.
Nugent was given a free header on the edge of the area and his knock-down fell to Ulloa, who blazed over from close range.
Early in the second half the Baggies had an opening when Berahino burst through the middle but he shot wide with Gardner screaming for a pass to his right.
Otherwise the half was uneventful, although Leicester were awarded a controversial free-kick when substitute Andy King went down under a Chris Brunt challenge.
Thankfully for Albion, Riyad Mahrez blazed it over the bar.
But there was no escape on 80 minutes when Huth's header gave Leicester their second equaliser.
The Baggies failed to deal with a Nugent cross, Marcin Wasilewski headed back across goal and Huth's goalbound effort was helped into the net by Craig Dawson's poor attempted clearance.
Albion continued to sit back and invite Leicester pressure and the Foxes always looked the more likely scorers.
The winner came in the first minute of stoppage-time as Vardy got the better of Gareth McAuley on halfway, raced away from Lescott and fired low past Myhill.