A flea market, also known as a swap meet, is a type of street market that provides space for vendors to sell previously owned (second-hand) goods. Flea markets are often held outdoors and comprise many vendors, including antique stores, businesses, churches, individuals, or anyone else who can rent a booth to sell their items. The items sold at flea markets can range from genuine, well-cared-for antiques to everyday household items. Flea markets may happen seasonally, weekly, monthly, or even as a one-off.

The origins of the term "flea market" are disputed, but one theory suggests that it is a common English calque from the French marché aux puces, which literally translates to "market with fleas," labeled as such because the items sold were previously owned and worn, likely containing fleas. Another theory suggests that the Fly Market in 18th-century New York City began the association, as the land on which the market took place was originally a salt marsh with a brook, and by the early 1800s, the Fly Market was the citys principal market.

Flea market vending is distinguished from street vending in that the market alone, and not any other public attraction, brings in buyers. There are a variety of vendors, including some who consider their work at flea markets a hobby due to their possession of an alternative job, and others who dedicate all their time to their stalls and collection of merchandise and rely solely on the profits made at the market.

Flea markets are becoming increasingly popular for sustainable consumption based on the reuse of all sorts of things. They offer an endless array of products that provide a more sustainable way to consume, based on recycling and saving money. The demand is mainly from young people searching for originality at a low price. Flea markets can be found in practically every big city, and they offer a unique shopping experience for those looking for interesting décor pieces, high-quality furniture, or vintage pieces for their homes.