Boldenone undecylenate, or boldenone 17β-undec-10-enoate, is a synthetic androstane steroid and a derivative of testosterone. It is the C17β undecylenate (undecenoate) ester of boldenone (δ1-testosterone, 1-dehydrotestosterone, or androsta-1,4-dien-17β-ol-3-one), which itself is the C1(2) dehydrogenated analogue of testosterone and a naturally occurring androgen found in the scent gland of Ilybius fenestratus (a species of aquatic beetle). Boldenone is the non-17α-alkylated variant of metandienone (17α-methyl-δ1-testosterone). An AAS related to boldenone undecylenate is quinbolone (δ1-testosterone 17β-cyclopentenyl enol ether).