Goals from Sadio Mane and Roberto Firmino in the first half gave table-toppers Liverpool a seemingly unassailable lead.
Luke Shaw sealed the points seven minutes from time before Jamie Vardy headed home a consolation for the visitors.
In six seasons at Leicester, Vardy, 31, has scored 88 goals and most memorably spearheaded the Foxes' incredible Premier League triumph in 2015/16.
Manchester United have to defy their own manager Jose Mourinho's fears for a season of doom and gloom when they kick off the Premier League campaign against Leicester City on Friday.
Ghezzal joined Lyon's academy at the age of 12, and signed his first professional contract with the club in 2010.
Javi Martinez nodded in from a corner on 59 minutes as the German champions overcame a lacklustre display from Jose Mourinho's side.
Harry Maguire will cost 65 million pounds with part of the outlay being offset by selling Argentinian defender Marcos Rojo.
The 27-year-old, a pivotal figure when Leicester stormed to a shock Premier League title in 2016, signed a five-year contract.
Champions Manchester City will have to wait until Sunday for their first outing.
The 30-year-old defender has signed a three year contract with the 'Foxes'
Chelsea manager Antonio Conte hailed his players' physical and mental strength to shrug off their Champions League disappointment.
Leicester ran a feature on Mahrez on their website looking at the impact of the player this season, suggesting the Facebook post was a hoax.
Manchester United host Brighton, whilst Chelsea visit Leicester in the FA Cup quarter-finals.
Sergio Aguero took centre stage with a finishing masterclass to take his tally in Manchester City's last seven home games to 14 goals.
Conte's side produced a limp display that could easily have seen them beaten by a Leicester team who missed a host of first-half chances.
The Clarets thought they had rescued a point when they equalised on the 87th minute, but Ragnar Klavan met Dejan Lovren's header in the final moments.
Mohamed Salah was again instrumental for Liverpool as he took his tally to 17 Premier League goals this season.
Manchester United paid for wasting some chances when Marc Albrighton crossed and Harry Maguire headed home in the final seconds.