The 31-year-old duplicated the feat of Yevgeny Kafelnikov in 1995 as he improved to a perfect 5-0 record over Haas, the ATP number 57.
The 65-minute final played in bright sunshine, which has characterized the summer clay week in this alpine village at 800 metres, marked the first trophy for Youzhny since 18 months ago in Zagreb.
He won his last on clay more than three years ago in Munich.
Despite hailing from flatland Holland, Haase has made his best results in similar conditions to Gstaad, winning the last two editions of the tournament in the Austrian ski resort of Kitzbuehel.
He was travelling there to begin his title defence next week.
"I had my biggest success in the mountains so far. It's not a coincidence since I also played well in Madrid. I'm really confident with both my serve and my return and that helps a lot," said the altitude-loving finalist.
"It was a difficult match, Mikhail's game definitely doesn't suit me. He showed his best form and years of experience today.
"It's so tough to play him, I've never beaten him and that kinda hurts. But I hope to get another chance."
Youzhny broke once per set, for 5-3 and the first and early in the second.
But he had to recover from 0-30 down as he served for victory, requiring three match points to get the job done.
"This feels really great," said the 12th player aged over 30 to win an ATP title in 2013. "Robin was a tough opponent but I was able to play my best tennis and beat him. It's been a super week for me.
"Even through I played a lot of my matches in the morning, the stands were relatively full even then. Every one of my matches was a tough one. It was a hard week but it ended very well."
The Russian lost a final last month in Halle on grass to Roger Federer, who along with compatriot and number 10 Stanislas Wawrinka had been billed as the anchors of the event.
But Federer, playing Gstaad for the first time in nine years, and ten-time participant Wawrinka both lost early due to back pain and face late fitness decisions if they are to play the Montreal Masters starting a week from Monday.
The final was played to a full house at a stadium fashioned annually from the local hockey rink in the centre of the pedestrianized village.
Youzhny won his ninth title from his 20th ATP final while Haase became the second Dutchman to play a Gstaad final after four from Tom Okker, 1968-71.