Adrenocorticotropic hormone (ACTH) or corticotropin is a hormone produced by the anterior pituitary gland that stimulates the adrenal cortex.

The six related peptides include smaller biologically active fragments (hormones) which are derived from a common precursor by differential processing of the pro-opiomelanocortin polyprotein (POMC) viz. ACTH, corticotrophin like intermediate lobe protein [CLIP], ß-endorphin, gamma-lipotropin [yLPH], met-encephalin and alpha-melanotropin [aMSH]1.

The properties of ACTH were first investigated in the 1930s. In 1933, research groups headed by James Collip, Herbert Evans and Bemardo Houssay used pituitary extracts to stimulate the adrenal cortex. American biochemist Choh Hao Li was one of several scientists who isolated ACTH in 1943 and synthesized it in 1963.