Italy is the country where many people eat lentils on New Year's Eve as a symbol of coins and prosperity.
Lentils are round and coin-like, so their appearance has encouraged an association with wealth and financial good fortune. In Italian New Year's meals, they are often served with cotechino or zampone, traditional pork products. The meal is commonly eaten around the transition into the new year or on New Year's Day, depending on household practice.
The custom is part of a wider group of European food traditions that connect round shapes, abundance, or harvest foods with prosperity. It does not mean that every Italian family follows exactly the same menu; regional cuisines and personal traditions vary widely.
Lentils are sometimes confused with the Spanish twelve-grape custom or the Italian red-clothing superstition. Those are separate traditions. Lentils represent prosperity through food, while red garments are associated with luck and love.