Sweat bee is the common name for any bees that are attracted to the salt in human sweat. In its strict application, the name refers to members of the Halictidae, a large family of bees that are common in most of the world except Australia and Southeast Asia, where they are only a minor faunistic element. In the United States, the common species are black, brown, red, or metallic green, and sometimes with yellow markings, and usually 1/4 to 1/2 inch (4-10 mm) in size. Their attraction to sweat makes them a nuisance, as they will sting if squeezed or squashed against one's flesh. Their sting is only rated a 1.0 on the Schmidt Sting Pain Index, making it almost painless. However, individuals with allergies to any kind of insect stings should seek immediate medical attention. Pest control is not recommended due to their beneficial nature in pollination.

As with many common names, however, the term "sweat bee" is applied colloquially to different insects in different continents, despite its technical restriction to halictids. Thus, in Africa and parts of Southeast Asia, the colloquial name is used to refer to what are technically known as stingless bees, which are typically in the genus Trigona and its relatives (family Apidae), and also have the habit of taking up salt from human perspiration. The European honey bee, Apis mellifera, also occasionally laps human perspiration, as will other bees on occasion.