Lawrence edged out Joost Luiten by one shot to add the Munich trophy to previous wins at the Joburg Open and European Open in 2022 and this year's South African Open Championship.
"It means a lot," said Lawrence, fighting back tears after becoming just the second South African to win at the German venue after Ernie Els.
"There's been a lot of hard work. I went to America for six weeks and 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.
He added: "I don't know why I'm so emotional but obviously it just shows that it means the world and to get my fourth victory in Germany is unbelievable."
After trailing by four overnight, the 17th hole proved critical on Sunday as Lawrence hit a stunning tee shot to set up a birdie while Dutchman Luiten three-putted the par three to drop out of the lead for the first time all day.
Lawrence parred the last for a 69 to finish at 13 under and with Luiten unable to make a birdie on the par-five, the tournament was over.
Luiten's closing 74 left him a shot ahead of New Zealand's Daniel Hillier, Japan's Rikuya Hoshino, Maximilian Kieffer of Germany and Poland's Adrian Meronk.