The main ingredient of pesto sauce is basil. This aromatic herb forms the foundation of traditional pesto, which is a green sauce originating from Italy, especially the Liguria region. Besides basil, classic pesto recipes typically include garlic, pine nuts, Parmesan cheese, and olive oil. The ingredients are blended to create a flavorful paste that can be used as a condiment or sauce for pasta, meats, or vegetables. Variations of pesto can substitute other herbs or nuts, such as parsley or walnuts, accommodating different tastes while maintaining the signature pesto characteristics of freshness and depth of flavor.