According to the charity, it wants to 'honor the many wise and wonderful vegans who have crested 50.'
The top prize is a free one-night stay for two people in the world's first all-vegan hotel suite, inside the five-star Hilton London Bankside Hotel.
"This competition celebrates the venerable vegans who are setting an example of compassion for the younger generations to follow," said PETA Director Elisa Allen.
"PETA can't wait to pay tribute to this vibrant community of animal rights proponents who are testaments to the power of vegan eating."
In addition to saving the lives of nearly 200 animals every year, people who go vegan could very well be extending their own lifespans, too, as vegans are less prone to suffering from heart disease, cancer, diabetes, and obesity and are, on average, fitter and trimmers than meat-eaters are.
One winner will be picked from all entrants - there are no gender categories so the winner could be male, female, or gender-non-conforming.
Those who enter must be at least 50 years of age and must enter by July 22.
A PETA panel will pick finalists, then open voting to the public, who will help pick the winner. Vote count will be one factor in who wins. The winner will be announced on August 12.