Nandrolone decanoate is a long-acting ester of nandrolone, an anabolic-androgenic steroid structurally related to testosterone. The decanoate ester allows gradual release following intramuscular administration.

Nandrolone preparations have had historical medical applications in selected conditions, although use varies considerably by jurisdiction and formulation.

Potential effects include suppression of endogenous testosterone and sperm production, changes in lipids and hematocrit, androgenic effects, and cardiovascular or reproductive complications.