FLIT is the brand name for an insecticide. The original product, invented by chemist Dr. Franklin C. Nelson and launched in 1923 and mainly intended for killing flies and mosquitoes, was mineral oil based and manufactured by the Standard Oil Company of New Jersey before the company, now part of ExxonMobil, was renamed first Esso and later Exxon. The Esso formulation contained 5% DDT in the late 1940s and early 1950s, before the negative environmental impact of DDT was widely understood. Later marketed as "FLIT MLO", it has since been discontinued. A hand-operated atomizer called a Flit gun was commonly used to perform the spraying.

The Flit brand name has been reused for another insecticide product, with the primary active ingredient of permethrin, marketed by Clarke Mosquito Control. The current product is most often used to control adult mosquitoes. Spraying it into the air kills adult mosquitoes that are present and then by settling onto surfaces it kills mosquitoes that may later land.