The 26-year-old from Vienna caught the long-time leader Thorbjorn Olesen with a burst of four birdies in five holes around the turn and then took the lead with two more birdies at the 15th and 16th.
He finished with a spectacular 50-foot putt on the final green for a 19-under-par total at Diamond Country Club in Atzenbrugg - only an hour away from his home.
Ireland's Shane Lowry posted a final-round 66 to share second place with Frenchman Thomas Levet two shots back.
Dane Olesen, who had led since midway through a rain-hit second round, slumped to a 74 to leave him a further two shots adrift in fifth place, one behind Sweden's Rikard Karlberg.
Victory saw Wiesberger become the second Austrian to win his national open after Markus Brier in 2006. It came just three months after his first European Tour victory at the Ballantine's Championship.
Any doubts over whether Wiesberger could hang on to his lead were dispelled at the 17th - when his mis-hit tee shot clattered into a tree but then bounced into short semi-rough to leave him an angle to the green to save his par.
A jubilant Wiesberger said the victory had made it "the best day of my life so far".
"It seems like it went my way, especially the last two holes," he told www.europeantour.com.
"I had such a great country and such great fans backing me. I'm very proud to be following in such big footsteps [as Brier]. I'm sure I'm not going to be the last home winner."