Oophorectomy (; from Greek ᾠοφόρος, ōophóros, 'egg-bearing' and ἐκτομή, ektomḗ, 'a cutting out of'), historically also called ovariotomy is the surgical removal of an ovary or ovaries. The surgery is also called ovariectomy, but this term is mostly used in reference to animals, e.g. the surgical removal of ovaries from laboratory animals. Removal of the ovaries of females is the biological equivalent of castration of males; the term castration is only occasionally used in the medical literature to refer to oophorectomy of women. In veterinary medicine, the removal of ovaries and uterus is called ovariohysterectomy (spaying) and is a form of sterilization.

The first reported successful human oophorectomy was carried out by (Sir) Sydney Jones at Sydney Infirmary, Australia, in 1870.

Partial oophorectomy or ovariotomy is a term sometimes used to describe a variety of surgeries such as ovarian cyst removal, or resection of parts of the ovaries. This kind of surgery is fertility-preserving, although ovarian failure may be relatively frequent. Most of the long-term risks and consequences of oophorectomy are not or only partially present with partial oophorectomy.

In humans, oophorectomy is most often performed because of diseases such as ovarian cysts or cancer; as prophylaxis to reduce the chances of developing ovarian cancer or breast cancer; or in conjunction with hysterectomy (removal of the uterus). In the 1890s people believed oophorectomies could cure menstrual cramps, back pain, headaches, and chronic coughing, although no evidence existed that the procedure impacted any of these ailments.

The removal of an ovary together with the Fallopian tube is called salpingo-oophorectomy or unilateral salpingo-oophorectomy (USO). When both ovaries and both Fallopian tubes are removed, the term bilateral salpingo-oophorectomy (BSO) is used. Oophorectomy and salpingo-oophorectomy are not common forms of birth control in humans; more usual is tubal ligation, in which the Fallopian tubes are blocked but the ovaries remain intact. In many cases, surgical removal of the ovaries is performed concurrently with a hysterectomy. The formal medical name for removal of a woman's entire reproductive system (ovaries, Fallopian tubes, uterus) is "total abdominal hysterectomy with bilateral salpingo-oophorectomy" (TAH-BSO); the more casual term for such a surgery is "ovariohysterectomy". "Hysterectomy" is removal of the uterus (from the Greek ὑστέρα hystera "womb" and εκτομία ektomia "a cutting out of") without removal of the ovaries or Fallopian tubes.