Androgen replacement therapy (ART), often referred to as testosterone replacement therapy (TRT) or hormone replacement therapy (HRT), is a form of hormone therapy in which androgens, often testosterone, are supplemented or replaced exogenously. ART is often prescribed to counter the effects of male hypogonadism. It typically involves the administration of testosterone through injections, skin creams, patches, gels, pills, or subcutaneous pellets.

ART is also prescribed to lessen the effects or delay the onset of normal male aging. However, this is controversial and is the subject of ongoing clinical trials. As men enter middle age they may notice changes caused by a relative decline in testosterone: fewer erections, fatigue, thinning skin, declining muscle mass and strength, and/or more body fat. Dissatisfaction with these changes causes some middle age men to seek ART. Androgen deficiencies in women have also, as of 2001, been recognized as a medical disorder that can be treated with ART. As with men, symptoms associated with androgen deficiency are most prevalent with age, and androgen replacement therapy has been shown to help with symptoms of menopause.