Lawrence carded eight birdies, five bogeys and five pars in a closing 69 as he finished 13 under par and overturned a four-shot deficit to Holland’s Joost Luiten.
Luiten managed just one birdie and three bogeys in a closing 74, crucially missing from two feet for par on the 17th before narrowly failing to convert a long-range birdie attempt on the last to force a play-off.
Lawrence had not recorded a top-10 finish since his previous victory on home soil in December and fought back tears in his post-round interview.
“It means a lot. I’m a bit emotional to be honest,” Lawrence told Sky Sports.
“I went to America for six weeks, made one cut. This game is not easy. It was a real boost today and I really gave it my all. I feel sorry for Joost, I know how tough this game is.
“I don’t know why I’m so emotional but it just shows it means the world and to get my fourth victory in Germany is unbelievable.
“I played really well today and at some stage I didn’t think I was going to make a par; it was birdie, bogey, birdie, bogey – you’re just taking, giving, taking, giving.
“I saw Joost miss that two-footer on 17 and I know how tough those putts are around these greens. It wasn’t easy out there so I feel for him.
“I think that’s why I’m emotional as well because I know how tough this game is and everybody wants to win.”
Seeking a seventh career victory and a first since 2018, Luiten began the day three shots ahead of compatriot Daan Huizing and recovered from a bogey on the third with a birdie on the fifth.
However, that proved to be his only birdie of the day and a bogey on the seventh was followed by nine straight pars before he three-putted the 17th, the same hole Lawrence had birdied minutes earlier.
Luiten’s drive on the 18th finished on the edge of a water hazard and he was able to pitch out on to the fairway and hit a good approach from 204 yards to 25 feet, but his birdie putt from the fringe trickled agonisingly wide.
Home favourite Max Kieffer, Adrian Meronk, New Zealander Daniel Hillier and Rikuya Hoshino shared third place on 11 under par.