While lifting the top-flight trophy at the King Power Stadium in May 2016 ranks as the Foxes' greatest day, Tuesday night's 2-2 draw with Hull City will go down as one of their worst as it confirmed a second successive relegation.
Gary Rowett's side briefly had dreams of a great escape as quickfire goals from Jordan James and Luke Thomas overturned Liam Millar's opener, but Oli McBurnie's strike midway through the second half left them seven points from safety with just two games to go.
"There are no excuses," Leicester chairman Aiyawatt Srivaddhanaprabha said in a statement.
"We have experienced the highest highs and now the lowest lows, and the pain is shared by all of us. I am truly sorry for the disappointment we have caused."
After one win in 18 games, the draw condemns them to the third tier for the first time since 2009 and memories of winning the Premier League under Claudio Ranieri, a run to the Champions League quarter-finals and an FA Cup victory will seem like distant memories.
Hull have plans on exiting the Championship through the front door, but they dropped to seventh and out of the playoff positions following Wrexham's 1-0 win at relegation-threatened Oxford United. The Welsh club are now sixth on goal difference.
Coventry City clinched the title with a convincing 5-1 victory over Portsmouth.
Frank Lampard's Sky Blues will return to the Premier League for the first time in 25 years after relegation at the end of the 2000-01 season.
And they celebrated at home with a brace from Ephron Mason-Clark, one each from Haji Wright and Kaine Kesler-Hayden and a Regan Poole own goal.
Former Sydney FC forward Adrian Segecic got one back for Pompey.
Another former A-League star in Mohamed Toure got on the scoresheet again for Norwich City.
The 22-year-old Socceroos striker, hoping to feature at this year's World Cup, fired the Canaries into the lead just after the half-hour mark having missed an early penalty in a 2-1 victory over Derby County.
It was Toure's ninth goal in 11 appearances since joining in January and dealt a huge blow to the Rams' dreams of reaching the playoffs – and kept their own hopes alive.
Norwich are six points adrift of the top six, while Derby are four behind Hull and Wrexham and, like the Canaries, need two wins and big favours from other teams to reach the playoffs.
Elsewhere, second-placed Millwall moved three points clear of Ipswich Town and Southampton in the race for automatic promotion after winning 3-1 at Stoke City.
The Saints are fourth, but were held to a 2-2 draw by Bristol City.
With AP & AAP.