甜菜碱是一种从甜菜中发现的生物碱，其分子式为C₅H₁₁NO₂。甜菜碱型物质可作为两性表面活性剂用于去污剂中。

Trimethylglycine (TMG) is an amino acid derivative that occurs in plants. Trimethylglycine was the first betaine discovered; originally it was simply called betaine because, in the 19th century, it was discovered in sugar beets. Since then, many other betaines have been discovered, and the more specific name glycine betaine distinguishes this one.