Pulque, or octli, is a fermented beverage made from the juice of the agave or maguey plant. Outside of Mexico, pulque can be difficult to obtain, because it is not very shelf-stable. Most consumers are more familiar with tequila, another alcoholic beverage made from agave, although tequila is fermented and distilled to make a strong alcohol, while pulque is more like a type of beer, with a relatively low alcohol content and a distinct sour flavor which comes from fermentation.

Agaves are succulents which are abundantly distributed across Mexico and the American Southwest. They are sometimes known as century plants due to their infrequent flowering cycle. The stalks of these flowers produce a sweet nectar which is collected to produce pulque. Most nectar used in pulque making comes from the Agave salmiana plant, which has been used as a source of nectar since the time of the Aztecs.

Pulque is fermented, not distilled. It was probably one of the earliest alcoholic beverages produced in Central America, just as beers were produced before liquors in other parts of the world. Pulque also plays a role in the traditional religions of Mexico and central America; with the discovery of pulque being credited to Tepoztecatl, an Aztec god. Pulque was also apparently enjoyed by gods of drunkeness, and some consumers sacrifice a small slop of pulque to the gods before drinking a glass of this traditional beverage.

The agave nectar used to make pulque is collected in large drums over a period of weeks and then allowed to ferment. As soon as the fermentation process is complete, the pulque is ready to drink. The flavor of the drink undergoes rapid changes once it is finished, making pulque can be hard to obtain outside of regions which produce this traditional thick, slightly milky drink. Some producers have managed to pasteurize and can their pulque for export, although purists cast aspersions on canned pulque.

The sour flavor can make pulque an acquired taste. The beverage is often mixed with other ingredients to make it more palatable. Pulque mixed with fruit juices like mango and pineapple is often found for sale as curado. In Mexico, the beverage can be found for sale at pulqueiras, bars devoted to the sale of pulque; traditionally, these establishments were restricted to men.