Aji is a term used to refer to chili peppers, particularly in South America and the Caribbean. The aji amarillo chili pepper is a member of the Capsicum baccatum species and is grown all over Peru. It is a key ingredient in Peruvian cuisine and is used in many classic Peruvian dishes, such as causa rellena and papa a la huancaína, as well as aji de gallina (Peruvian spicy creamed chicken) . Aji amarillo is also used in many sauces, where it adds a bright complex flavor as well as its distinctive yellow/orange color.

Ají sauce is a spicy sauce made from ají peppers that is usually served to accompany other dishes in a variety of Latin American cuisines. Its most basic ingredients include ají peppers, water, oil, garlic, cilantro, and salt. Ingredients are usually blended together using a blender or food processor. Although ají sauce recipes can vary from person to person, there are generally country-specific and region-specific varieties).

In Ecuadorian cuisine, ají amarillo, onion, and lemon juice (amongst others) are served in a separate bowl with many meals as an optional condiment. In Colombian, Peruvian, and Ecuadorian cuisines, ají sauce is also a common condiment.