扁桃苷（Amygdalin，源自希腊语“扁桃”ἀμυγδάλη amygdálē ），又名苦杏仁苷，是1803年Pierre-Jean Robiquet与A. F. Boutron-Charlard从扁桃的种子中分离出的一种糖苷。李比希与维勒于1830年对这一物质进行了研究。扁桃苷也存在于其他的李属植物，包括杏和黑樱桃中，也存在于枇杷的叶、果和核里。恩斯特·T·克雷布斯（Ernst T. Krebs）曾将这一物质命名为“维生素B17”，并认为可以治疗癌症，但随后的研究证明这一物质并不具有上述功效。学界也不认为苦杏仁苷是一种维生素，因为苦杏仁苷并不符合维生素的定义。

Amygdalin (from Ancient Greek: ἀμυγδαλή amygdálē "almond"), is a poisonous cyanogenic glycoside found in many plants, but most notably in the seeds (kernels) of apricot (known as bitter almonds ), peach, and plum.

Since the early 1950s, both amygdalin and a modified form named laetrile have been promoted as alternative cancer treatments, often using the misnomer Vitamin B₁₇ . But studies have found them to be clinically ineffective in the treatment of cancer, as well as potentially toxic or lethal when taken by mouth, due to cyanide poisoning. Neither amygdalin nor laetrile is a vitamin.