While downhill expert Kilde appeared to have full control of the Saslong piste in Val Gardena, late starter Bennett disrupted the proceedings by flawlessly executing the final part, finishing 0.03 seconds ahead of his rival.
Bennett, wearing bib number 34, completed the course under perfect conditions with sunny skies and a fast, well-prepared track in one minute 23.80 seconds and took his second career World Cup triumph.
Marco Odermatt from Switzerland was third, 0.05 seconds behind Bennett.
"I did not expect the green light - I wanted to put down a run that I was going to be proud of, and I left everything on the hill," Bennett said.
"If I ever win the downhill globe (the season trophy), you will never see me ever again. I am boots off in the finish, on a plane, fishing boat in Mexico," he added with a smile.
The next race for the men will be the super-G on Friday.
