A yeast is a eukaryotic and single-celled microorganism.
Yeast may also refer to: Baker's yeast, yeast used as a leavening agent in baking Yeast extract, food product from processed yeast Yeast (novel), aka Yeast: A Problem, an 1848 novel by Charles Kingsley Yeast (journal), a monthly peer-reviewed scientific journal Yeast (wine), the role of yeast in winemaking