The Lurgan born boss praised heroes Fraser Forster, Victor Wanyama and Tony Watt after the side completed the memorable Group G win in Glasgow on Wednesday night.
Parkhead exploded in the 21st minute when midfielder Wanyama headed in from a Charlie Mulgrew corner.
And in the 83rd minute 18-year-old Watt, on for Mikael Lustig to make his debut in the competition, raced away to score the second, leaving Lionel Messi's late strike a consolation in injury time.
Forster reprised his stunning display from the narrow 2-1 defeat to the same opposition two weeks ago, making a string of excellent saves and even claiming the assist as Watt grabbed his goal.
Lennon said: "I think it was one of the greatest nights in the club's recent history.
"It was very poignant at our 125th anniversary, one to play Barcelona in such a prestigious game and two, to win the game under huge difficulties with the squad decimated by injuries and illness."
The players are heroes, they are heroes to me, I can't speak highly enough of their performance tonight and they will go down in the history books of the club as the team who beat probably the best team in the world.
"Everyone goes on about tactics but football is about players and they have covered themselves in glory tonight," he said.
Lennon also praised young Watt who is fast becoming a favourite of the Celtic fans.
He said: "It is a memorable thing he has done so early in his career.
"I said before the game I had no hesitation in playing him, I just thought his lack of experience would have been too much to put him in the starting line-up but everything we asked him to do, he did.
"He scored a brilliant goal and should have had a penalty and a sending-off when he got on Mascherano's wrong side.
"He is learning, he wrote himself into the history books of the club but he is 11 games into his career.
"I hope he has a fruitful career but tonight will take some topping."
Watt said: "It'll take a couple of hours to sink in. I just saw (Victor) Valdes, I thought to put it to the side of him and it might go in.
"It's probably the best moment of my life, I'll look back at it when I'm older and think 'We've just beaten Barcelona in the Champions League' - there's nothing better."
It's tremendous, I don't think words can describe it.
Celtic remain in a strong position to qualify for the knockout stages of the competition, with seven points from four games, two less than leaders Barca. They next travel to Benfica before hosting Spartak Moscow in their final group fixture.
Benfica have four points following their home win over Spartak Moscow, who are bottom of the group with three points.
Lennon said: "We have a chance, that's all it has given us. A greater chance than maybe we expected before the game.
"But we still have two very tough games.
"The problem is the players and staff will have to deal with is that the expectation level will increase.
"There is still a lot of work to do but we have given ourselves a platform.
"But that's for the future, I want the players to enjoy the moment and take it all in."
As they did when they came back from a goal behind in the Nou Camp last month to win 2-1 against Celtic, Barcelona dominated possession.
Barca coach Tito Vilanova said: "First of all I would like to congratulate Celtic, the fans were amazing tonight.
"If we had scored first it might have been a different game.
"But they scored first which allowed them to defend and their goalkeeper was brilliant tonight.
"It is not the first time we have lost a game like this and it won't be the last."