Galactorrhea (also spelled galactorrhoea) (galacto- + -rrhea) or lactorrhea (lacto- + -rrhea) is the spontaneous flow of milk from the breast, unassociated with childbirth or nursing.

Galactorrhea is reported to occur in 5–32% of women. Much of the difference in reported incidence can be attributed to different definitions of galactorrhea. Although frequently benign, it may be caused by serious underlying conditions and should be properly investigated. Galactorrhea also occurs in males, newborn infants and adolescents of both sexes.