The championships concluded with the elite and junior downhill competitions for both women and men, with total attendance over the five days of events reaching 65,000 – a record for mountain biking.
The elite women's competition was expected to be a battle between British teammates Atherton and Tahnee Seagrave, who battled all season on the World Cup circuit and finished 1-2 in qualifying.
Morgane Charre of France set the first sub-3:40 time, which stood until Swiss rider Emilie Siegenthaler knocked three seconds off.
Two French riders – Marine Cabirou and Myriam Nicole – took the lead in quick succession, with Nicole taking the lead time down to 3:26.
Seagrave then knocked another 0.7 seconds off, and then it was down to Atherton, who was clearly riding at a different level.
She was three seconds ahead at the first split, six seconds up at the second, and a staggering 9.983 seconds up by the finish.
"It hasn't really sunk in yet," said Atherton. "I knew it was going to be a hard race and that I had to be fast. All the way down I thought I was going to crash.
"Coming into the finish, I could hear the announcer saying I was the 2018 world champion, and I just had to push right to the end. It's hard, because we train earlier in the day when the light is different, so it was hard to see the lines during the race."
The junior women's race was won by Austria's Valentia Holl.
Full results to follow