Aspartame (or APM) (pronounced /ˈæspərteɪm/ or /əˈspɑrteɪm/) is an artificial, non-saccharide sweetener used as a sugar substitute in some foods and beverages. In the European Union, it is codified as E951. Aspartame is a methyl ester of the aspartic acid/phenylalanine dipeptide. It was first synthesized in 1965.

The safety of aspartame has been the subject of several political and medical controversies, Congressional hearings and internet hoaxes since its initial approval for use in food products by the U.S. Food and Drug Administration (FDA) in 1974. A 2007 medical review on the subject concluded that "the weight of existing scientific evidence indicates that aspartame is safe at current levels of consumption as a non-nutritive sweetener".[3] However, because its breakdown products include phenylalanine, aspartame must be avoided by people with the genetic condition phenylketonuria (PKU).