Androstanes are a class of steroidal compounds that have a basic structure consisting of a four-ring core derived from cholesterol. Specifically, androstanes contain a 19-carbon skeleton with a chemical formula of C19H28O or C19H28O2, depending on whether they are alcohols (androgens) or ketones (androstanes), respectively.

The term "androstane" is often used to refer to the parent compound, which has a hydroxyl group (-OH) attached at the C3 position of the steroid nucleus. When this hydroxyl group is replaced by a keto group (-C=O), the resulting compound is called androstane-3,17-dione or simply "androstane."

Androstanes are important precursors in the biosynthesis of various steroid hormones, including testosterone, estrogen, and cortisol. They are also used as intermediates in the synthesis of certain drugs and pharmaceuticals.