Fleischmann's Yeast is an American brand of yeast founded by Hungarian-American businessman Charles Louis Fleischmann. It is currently owned by Associated British Foods and is sold to both consumer and industrial markets in the United States and Canada.

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.