People for the Ethical Treatment of Animals (PETA) recognised the fast-food chain at its eight annual Vegan Food Awards.
The KFC Original Recipe Vegan Burger won the Best Vegan Chicken category.
Launched in June 2019, it consists of a bespoke Quorn fillet coated in herbs, iceberg lettuce, and vegan mayonnaise in a glazed bun, and was originally called The Imposter.
During its trial period, it sold out within four days of being released in the UK.
At the time, a branch in London said it was selling one approximately every minute.
KFC also said sales were 500% higher than its classic chicken burger around the time it came out.
Dawn Carr, PETA's director of vegan corporate projects, said: "While the world battles a deadly disease that came from a meat market, it's no surprise that vegan food is booming.
"The winners of PETA's Vegan Food Awards are making it easier than ever to go vegan by dishing up everything from creamy dairy-free ice cream to satisfying vegan fried chicken."
She added: "The pandemic has demonstrated that widespread societal change is possible, and that includes the explosive growth in the already booming demand for vegan foods."
Other winners included Tesco's Plant Chef range, OGGS Victoria Sponge Cakes, Papa John's "The Vegan Works" pizza and Nando's Perinaise sauce - there were 24 categories in total.