After breaking free in the final 15 kilometres, the Commonwealth champion clocked a winning time of 2 hours, 8 minutes, and 53 seconds on the streets of Budapest.
Maru Teferi, an Ethiopian-born Israeli, finished second in 2:09.12, while Ethiopian Leul Gebresilase took bronze (2:09.19).
“This has been my dream, and it has finally come true,” Kiplangat said.
“Last year I was Commonwealth Games champion, and that made me think this year I must become world champion. Now my prayers have been answered, and hopefully next year in Paris I will become an Olympic champion too.”
Kiplangat added: “It was hard today because it was so hot but I felt comfortable because I prepared well for this weather. I knew it was possible because I had trained well.”
Kiplangat and teammate Stephen Kissa, as well as Ethiopians Gebresilase, Tsegaye Getachew, Tamirat Tola, and Kenya’s Timothy Kiplagat, completed the 30-kilometre mark in 1 hour, 32 minutes.
Kissa then collapsed after tripping over Kiplagat’s heel, allowing Kiplagat to move clear with Gebresilase.
Over the next 5 kilometres, Kiplangat, 23, surged to successfully drop the lead pack, with Gebresilase trailing 15 seconds behind.
“When I reached 30 km, I knew I felt strong and decided to push,” said Kiplangat. “I had great energy, and that allowed me to go. Then, at 35 km, I could surge again.
“That was always my plan, and I managed to do it. The pace was high, but I had more to give. It was tough, but I always felt I had the power.”
Teferi advanced through the field to take silver, while reigning world champion Tola, who set a championship record in Eugene last year, withdrew.
Kissa recovered well from his fall to finish fifth, just behind Lesotho’s Tebello Ramakongoana.
Teferi, who suffered a torn running top after collapsing around the 30km mark, said the hot weather had made it “very difficult for everybody.”
“I am grateful I managed to finish with the silver,” he said. “I wanted to get the best out of me, and this competition was my biggest target. I am glad I managed to fulfill my dream.”
Ethiopia’s defending champ, Tola, said he pulled out because of stomach pains.
“I was trying my best. I was feeling good until 30km,” he said. “But after that, I started to have a bad feeling in my stomach.
“I did not sleep the whole night because I had a problem with my stomach and I was about to puke, but nothing came out because I ate rice with a lot of salt.”