thumb|right|150px|Androstenedionethumb|right|150px|Androsteronethumb|right|150px|EstroneA ketosteroid, or an oxosteroid, is a steroid in which a hydrogen atom has been replaced with a ketone (C=O) group.
A 17-ketosteroid is a ketosteroid in which the ketone is located specifically at the C17 position (in the upper right corner of most structure diagrams).
Examples of 17-ketosteroids include:
17-Ketosteroids are endogenous steroid hormones.