Dumoulin, 26, became the first Dutchman in the race's 100 editions to win. He dislodged leader Nairo Quintana (Movistar), who was the first Colombian to win in 2014, in stage 21's time trial today in Milan.
"No, I never expected to win the Giro," Dumoulin said dressed in pink. "Maybe somewhere in the future, maybe one time with a lot of luck or whatever, but not this year. I would have been very happy with a place in the top ten."
Dumoulin looked relax as he sat eating a slice of pizza bought at a nearby shop by his mother in the shadow of Milan's famous Duomo cathedral.
Dumoulin gained on his rivals in the two time trials. He then managed himself in the mountains, sometimes limiting his loses with regular riding and sometimes attacking like on the stage to Oropa.
However his Giro d'Italia will probably be best remembered for the stomach problems he had on stage 16, forcing him to stop for a natural break at a crucial point in the action.
"I still made history by s***ting in the wood but now in a positive way. I will go down in the history books for winning the Giro after pooping in the woods, it's quite amazing," Dumoulin explained.
"I lost only two minutes in the last 30 kilometres, actually only 40 seconds after my incident, so after that, I thought, 'Maybe I'm better than I thought.' But it was still a long way. Although I knew there was still the time trial."
Watch: Giro d'Italia stage 21 highlights
Dumoulin turned a 53-second deficit into a 31-second lead to move into the pink jersey in Piazza del Duomo. He finished second to stage winner Jos Van Emden (LottoNL-Jumbo) with a time of 33-23. Quintana clocked 34-47.
"It's great. I don't now what to say. This is a dream come true," he continued.
"When I crossed the line, they said, you won! You won! Then it was only three seconds. I was freaking out. It was incredible. This is crazy. I could not have imagined this, never. I was strong, I was lucky, everything fell into the place during the Giro.
"I won it, it's incredible. I was feeling good, but halfway through the time trial, in my ear piece, they said, 'Don't take any more risks.' And I thought, OK, I must be winning. They should never do that again, because when I crossed the line, it was still so close."
The time blasted him from fourth to first overall. Nairo Quintana slipped to second and two-time champion Vincenzo Nibali (Bahrain-Merida) slipped from second to third overall.
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Gregor Brown is an experienced cycling journalist, based in Florence, Italy. He has covered races all over the world for over a decade - following the Giro, Tour de France, and every major race since 2006. His love of cycling began with freestyle and BMX, before the 1998 Tour de France led him to a deep appreciation of the road racing season.
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