The Australian started the day three shots behind his play-off rivals at The Renaissance Club but burst into contention thanks to birdie blitz from the third, where he picked up six consecutive shots.
Detry reclaimed the lead at 18 under at the 13th but the Belgian was desperately unlucky as the hooter sounded for a 90 minute delay for thunder and lightning as he was mid-swing for a par putt at the 14th and missed the effort to slip back.
Lee nudged back ahead with a birdie at the 16th, but the final pair followed suit to force a play-off.
The 22-year-old was inches from holing a closing putt for a gain which would have sealed his second European Tour title following his success at the 2020 ISPS Handa Vic Open, but he only needed one extra hole to secure the biggest win of his career.
With victory, Lee also secured one of the three places on offer at next week’s Open Championship at Royal St George’s Golf Club alongside Detry and Englishman Jack Senior.
“It’s an awesome day, I was pretty proud of how I played. Six birdies in a row, that was sweet. It kind of happened really quick,” an emotional Lee said.
“I could have holed a few more putts, in regulation I missed it by a roll, that was painful but we regrouped and the tournament starts in the play-off, pretty much.
“It’s just crazy, I’ve kind of dreamt of it last night and people back home staying up late to watch me, sending messages. This one is for you too.
“I hit a lot of good shots today, that was just one of them. In that situation, it’s a huge moment but I hit so many great shots.
“I’ve been playing really good in recent weeks and just trending, a few mistakes over the whole tournament and wasn’t able to capitalise so it’s awesome to do it here. I’ll enjoy this one.”