Seven years to the day after Celtic beat Barcelona 2-1 at Celtic Park, the club came from behind to beat Lazio and secure a place in the Europa league last 32.
Oliver Ntcham's 95th-minute striker sealed the historic win and qualification with two games to spare.
"This team just keeps setting new boundaries," said Lennon.
"I'm so proud of them, not just for winning the game, but the way they played - the character, the bravery and above all else, real quality.
"My goalkeeper made some great saves, which he is paid to do and he's done before, and my centre-half was incredible."
"Edouard had their back three in all sorts of trouble and Forrest came up with a huge goal - he was brilliant."
Lennon also hailed club captain Scott Brown for "playing some of the best football of his career".
"People talk about retiring, there's no way. He's got so much more to come in the next year to 18 months.
"He's one of the finest captains in the club's history. You see his performance tonight - that's the embodiment of what Scott Brown brings to Celtic."
Brown also praised the club's "exceptional" of qualifying with two games to spare.
"I think a lot of people would've written us off early doors with the Champions League elimination, but we've come back stronger, fitter and sharper," Brown told BBC Scotland.
"It's the first time any Celtic team has won against an Italian side in Italy so it means a lot. The lads had to dig deep at some points but we used our pace and quality on the counter-attack to win the game."