Dartos, the smooth muscle layer just deep to the skin of the scrotum; from the Greek, dartos, skinned or flayed.

The term was first used by Greek physicians for any anatomical preparation in which the skin had been removed. The first-century Romans, for reasons unclear, began using the term only for the muscle seen after removal of the skin of the scrotum; the name stuck.

When exposed to cold the dartos contracts. The scrotal skin wrinkles, the exposed surface area is reduced, and heat loss is minimized. Thus the muscle helps to regulate the all-important testicular temperature (and working with the spermatic cord's cremaster muscle which contracts to pull the testes towards the warm abdominal wall).

In females, a homologous muscle called the "dartos muliebris" (muliebris is Latin for "womanly") is found beneath the skin of the labia majora and is much less developed than the male counterpart. Its function probably rivals that of male nipples in importance.