Pét-nat, Pétillant Naturel, or Méthode Ancestrale, is a method of sparkling wine production used all over the world. Unlike traditional-method sparkling wines, like Champagne, which add sugar and yeast to dry, still wine in order to trigger a second fermentation and produce bubbles, pét-nat works by bottling wine that is only partially fermented.

As the first and only fermentation continues in the bottle, the resulting carbon dioxide (CO₂) is trapped. After a period of rest that can be as short as a couple of months, the gas is absorbed into the wine as bubbles and the pét-nat is ready to drink.