A progestogen, also referred to as a progestagen, gestagen, or gestogen, is a type of medication which produces effects similar to those of the natural female sex hormone progesterone in the body. A progestin is a synthetic progestogen. Progestogens are used most commonly in hormonal birth control and menopausal hormone therapy. They can also be used in the treatment of gynecological conditions, to support fertility and pregnancy, to lower sex hormone levels for various purposes, and for other indications. Progestogens are used alone or in combination with estrogens. They are available in a wide variety of formulations and for use by many different routes of administration. Examples of progestogens include natural or bioidentical progesterone as well as progestins such as medroxyprogesterone acetate and norethisterone.

Side effects of progestogens include menstrual irregularities, headaches, nausea, breast tenderness, mood changes, acne, increased hair growth, and changes in liver protein production among others. Other side effects of progestogens may include an increased risk of breast cancer, cardiovascular disease, and blood clots. At high doses, progestogens can cause low sex hormone levels and associated side effects like sexual dysfunction and an increased risk of bone fractures.

Progestogens are agonists of the progesterone receptors (PRs) and produce progestogenic or progestational effects. They have important effects in the female reproductive system (uterus, cervix, and vagina), the breasts, and the brain. In addition, many progestogens also have other hormonal activities, such as androgenic, antiandrogenic, estrogenic, glucocorticoid, or antimineralocorticoid activity. They also have antigonadotropic effects and at high doses can strongly suppress sex hormone production. Progestogens mediate their contraceptive effects both by inhibiting ovulation and by thickening cervical mucus, thereby preventing fertilization. They have functional antiestrogenic effects in certain tissues like the endometrium, and this underlies their use in menopausal hormone therapy.

Progesterone was first introduced for medical use in 1934 and the first progestin, ethisterone, was introduced for medical use in 1939. More potent progestins, such as norethisterone, were developed and started to be used in birth control in the 1950s. Around 60 progestins have been marketed for clinical use in humans or use in veterinary medicine. These progestins can be grouped into different classes and generations. Progestogens are available widely throughout the world and are used in all forms of hormonal birth control and in most menopausal hormone therapy regimens.