What ingredient gives traditional aioli its characteristic pungent flavor?

Garlic

Traditional aioli is a Mediterranean sauce made by emulsifying garlic with olive oil, often using a mortar and pestle to release the pungent oils. The name itself comes from the Catalan and Provençal words for 'garlic' (all) and 'oil' (oli). While modern versions often use mayonnaise as a base, the original recipe relies entirely on the emulsification of crushed garlic and oil to create its creamy texture.