Jungels (Quick-Step Floors) became just the second rider from Luxembourg to win a stage in the Giro after claiming victory in the 199-kilometre stage from Valdengo to Bergamo.
"It's not easy to realise but I'm super happy with this victory," Jungels said in quotes reported on www.giroditalia.it.
"I knew I had good legs today as I felt good in the climbs.
"I tried my luck in the final climb but it was a bit longer than I expected. In the downhill I was in a perfect position, on the wheel of (Domenico) Pozzovivo for sprinting.
"This is my first sprint victory. To do it at the Giro in front of these guys is wonderful."
Nairo Quintana (Movistar) took second to claim a six-second time bonus and reduce his overall deficit to Dumoulin to two minutes 41 seconds.
Dumoulin (Team Sunweb) said: "It was a hard day at a very high average speed. There were a lot of breakaways but always some teams weren't happy with it.
"Eventually after 110km, a group went. Then it was a very hard finale with a lot of favourites attacking but we stayed calm and it was a good day for us."
Britain's Adam Yates (Orica) finished fourth on the stage to move up from 13th to 11th in the general classification.
Estonia's Tanel Kangert, who started the day in seventh, was forced out of the race after suffering a fractured elbow following a crash into a bollard 10km from the finish.
Monday is a rest day ahead of Tuesday's stage from Rovetta to Bormio.
Stage 15 result:
1 Bob Jungels (Lux) Quick-Step Floors 4hrs 16mins 51secs
2 Nairo Quintana (Col) Movistar Team at same time
3 Thibaut Pinot (Fra) FDJ
4 Adam Yates (Gbr) Orica-Scott
5 Domenico Pozzovivo (Ita) AG2R La Mondiale
6 Patrick Konrad (Aut) Bora-Hansgrohe
7 Vincenzo Nibali (Ita) Bahrain-Merida
8 Tom Dumoulin (Ned) Team Sunweb
9 Ilnur Zakarin (Rus) Katusha-Alpecin
10 Bauke Mollema (Ned) Trek-Segafredo
Overall standings:
1 Tom Dumoulin (Ned) Team Sunweb 15hrs 48mins 8secs
2 Nairo Quintana (Col) Movistar Team at 2mins 41secs
3 Thibaut Pinot (Fra) FDJ at 3mins 21secs
4 Vincenzo Nibali (Ita) Bahrain-Merida at 3mins 40secs
5 Ilnur Zakarin (Rus) Katusha-Alpecin at 4mins 24secs
