The England goalkeeper kept his 11th consecutive clean sheet to break the long-standing record held by Charlie Shaw, who managed 10 in both the 1913/14 and 1921/22 seasons.
A Kris Commons strike in the fifth minute proved enough for all three points, and Lennon was proud of Forster and his defence for setting a new club benchmark.
"It's something that we're all very proud of, I'm sure particularly Fraser," Lennon said.
"We certainly don't take it for granted. These are special times for the players, when they look back on their time here they can look at that as quite an achievement.
"It's been a long time coming. To break (the record) is fantastic."
The Celtic manager was delighted with his side's overall performance, and singled out debutant and man-of-the-match Stefan Johansen for special praise.
"I was really pleased with the performance. Our football at times was fantastic and we were in total control of the game," he added.
"There were some great performances, particularly Johansen on his debut. It's as good a debut as I've seen in my time as manager here, so I really enjoyed watching us play.
"The only thing that was missing was a couple of more goals, which would have really emphasised our superiority in the game."
Forster is now only four games away from the world record for consecutive clean sheets, and Lennon said: "It's something to aim for.
"It's something that really keeps our season alive, I think we're pretty clear in the league now, so that's a yardstick for the players to try to achieve. That and keeping the unbeaten record going. That's 24 games and I can't ask any more of them really.
"We've just hit a really good vein of form in terms of our football, and I'm enjoying the way we are moving and passing the ball."
St Mirren manager Danny Lennon insisted his side were unfortunate to leave Parkhead empty-handed, and he was happy with the performance.
"We're disappointed," he said. "When you speak about the game-plan and you go out and lose a goal like that, especially when you know what the strengths of Commons are, Marian Kello's disappointed in it.
"The positive after the goal was that the players didn't let it affect them. They still continued to go out there and believe in themselves. I was very encouraged by the performance."