Shinkwin carded a closing 70 on Sunday to finish 12 under par at Celtic Manor, where he has now finished first, fourth and eighth in his last three visits.
A late charge from Scotland's Connor Syme secured second place on eight under, with Julien Guerrier, Andy Sullivan, David Dixon, Renato Paratore and Lucas Bjerregaard sharing third another three strokes back.
Daniel Hillier of New Zealand finished on three over par in a share of 35th place, and his compatriot Josh Geary ended six over. Dimitrios Papadatos, the sole Australian, finished on 11 over par.
Guerrier had trailed Shinkwin by a shot after 54 holes and fell further behind with a bogey on the first, but immediately got on level terms thanks to a birdie on the second as Shinkwin bogeyed.
However, Guerrier then dropped shots on each of the next three holes and Shinkwin rolled in a hat-trick of birdies from the fourth to establish what proved to be an unassailable six-shot lead.
"I'm just over the moon that I played great and finished it off," said an emotional Shinkwin, whose previous win came in the Aphrodite Hills Cyprus Open in 2020.
"Everyone was asking if it was match play between me and Julien. I chose not to try and do that because this golf course doesn't really reward match play.
"(Syme) sort of came out of nowhere. He was six, seven back and then obviously made a couple of birdies, (including) a good putt on 16 where I made bogey.
"And him hitting it in close when I've struggled at the 17th all week; for me to hole that (par) putt to guarantee a three-shot lead going down the last was huge."
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