Jacob Kiplimo later won the men's title for Uganda but only the approach of a thunder storm about to sweep over the Mount Panorama race track was able to offer drama comparable to the women's race.
World 10,000m champion Gidey had broken for the front on the final climb out of the swampy "Billabong" section of the course and looked to be coasting to the line when Chebet put on a late burst and appeared on her shoulder.
Ethiopian Gidey tried to react but her legs gave way and she fell to the ground as world 5,000m silver medallist Chebet swept past her and crossed the line in 33 minutes 48 seconds.
"I did not expect to win but I hung in," said Chebet, who won the under-20 title at the last championships in Aarhus in 2019.
"I saw that towards the finish Gidey was a bit slower and I ran hard and I won. When we were running, I thought that she was not running fast anymore and I thought I have the potential to go and win."
Tsigie Gebreselama of Ethiopia took the silver in 33.56 and Agnes Jebet Ngetich took bronze for Kenya in 34 minutes dead. Gidey had to be helped over the line and was disqualified.
Kiplimo finished second behind compatriot Joshua Cheptegei four years ago in Aarhus but raced clear of the leading pack on the final lap of the 2km circuit to win gold in 29.17.
Twice champion Geoffrey Kamworor of Kenya claimed a second successive silver in 29.26, while Olympic 5,000m and world 10,000m champion Cheptegei had to be satisfied with the bronze in 29.37.
"First place is very nice, I think I really wanted to win this time," said Kiplimo.
"I think my tactics were the best. I want to win another gold medal for my country. That's my mission."
Cheptegei, whose 2022 season was disrupted by injury, said he was content with bronze and would now turn his focus to defending his 10,000m title at the track and field world championships in Budapest in August.
"I normally don't like windy conditions so I think I am satisfied with the result," he said. "I am very happy for Jacob."
Both senior races were moved forward to try and beat the approaching storm but the athletes had to battle brutal heat as well as the innovative features on what had been described as the toughest course put together for a cross country worlds.
"I would have to say I'd take a half marathon or a marathon every day of the week," said Australian Isobel Batt-Doyle, who finished 29th in the women's race.
"This has to be the hardest race I've ever done. It was so hard all the way through."
A late burst earned Ethiopian Senayet Getachew the women's under-20 crown in 20.53, while Ishmael Kipkurui gave Kenya more success with a run of 24.29 to win the men's age-group race.
Kenya earlier dominated the mixed team relay ahead of Ethiopia in 23.14 with Australia giving the locals something to cheer about with a bronze medal.
