Mayonnaise is a creamy condiment made by emulsifying egg yolks, oil, vinegar (or lemon juice), and seasonings like salt and mustard. The process begins by slowly whisking or blending oil into egg yolks to create a stable emulsion. The vinegar or lemon juice is then added to provide acidity and flavor, while the mustard helps to stabilize the emulsion and add a slight tang. The result is a thick, smooth sauce that is often used as a spread, dressing, or dip.

The creation of mayonnaise is believed to date back to the mid-18th century. One widely accepted story is that it was invented in 1756 by the French chef of the Duke de Richelieu. The chef was preparing a victory feast in the town of Mahón, Spain, and, in the absence of cream, he created a sauce using eggs and oil, which he named "Mahónaisse" after the town. The sauce gained popularity in France, and over time, it evolved into the mayonnaise we know today.

Mayonnaise's rise in popularity continued into the 19th century, particularly in Europe and the United States, where it was commercialized.