The goal secured his position in the club's history as their first-ever scorer in the competition, and their first in Europe since 2000.
"It was some feeling, something I never thought I'd achieve," said Albrighton, who has won a Premier League medal, played against Barcelona and now scored in the Champions League since being released by Aston Villa two years ago.
"There is no reason why we can't win this competition," he added. "People said we couldn't win the Premier League but just to be this far is fantastic."
The game was effectively settled as a contest on 29 minutes when Mahrez curled a superb free kick into the net after veteran defender Timmy Simons had hauled down Jamie Vardy on the edge of the area.
With such a comfortable lead, Leicester began to savour the novel experience of playing top-level European football and could have added a third before the interval when Danny Drinkwater rocked back on his heels and produced a stinging volley from outside the area.
The only sour note for Leicester was a booking for 29-million-pound ($38.38-million) record signing Islam Slimani for a push on the back of Bjorn Engels, which led to the defender falling awkwardly and injuring his shoulder.
Mahrez completed the rout from the penalty spot on 61 minutes after Vardy gave the defence the slip and was upended by keeper Ludovic Butelle.
Leicester enjoyed such dominance that manager Claudio Ranieri substituted both strikers with 20 minutes remaining. The Italian said he was delighted with the performance, particularly on the back of last Saturday's 4-1 demolition by Liverpool.
"It was an important win after that Liverpool defeat," said Ranieri who has taken his teams out of the group stages in four of his five previous Champions League campaigns.
(Editing by Clare Fallon)
