Aspartame (or APM) is the name for an artificial, non-saccharide sweetener, aspartyl-phenylalanine-1-methyl ester; I. E., a methyl ester of the dipeptide of the amino acids aspartic acid and phenylalanine.

This sweetener is marketed under a number of trademark names, including Equal, NutraSweet, and Canderel, and is an ingredient of approximately 6, 000 consumer foods and beverages sold worldwide. It is commonly used in diet soft drinks, and is provided as a table condiment in some countries. It is also used in some brands of chewable vitamin supplements and common in many sugar-free chewing gums and has now been found in some chewing gums that are not sugar free. However, aspartame is not always suitable for baking because it often breaks down when heated and loses much of its sweetness. In the European Union, it is also known under the E number (additive code) E951. Aspartame is also one of the sugar substitutes used by people with diabetes.

Because sucralose, unlike aspartame, retains its sweetness after being heated, it has become more popular as an ingredient. This, along with differences in marketing and changing consumer preferences, has caused aspartame to lose market share to sucralose.