For the musical group, see Cul de Sac (group). See also Dead end (disambiguation).

A cul-de-sac (originally in anatomy: French, literally "bottom of a sack") or dead-end is a street or road with only one entrance and exit. While some are true cul-de-sacs, with no passage possible, others allow cyclists, pedestrians etc. to pass.

In modern urban planning cul-de-sacs are deliberately created as they are streets with very little traffic, and hence often desirable as residential areas.

Both cul-de-sac and dead end are used metaphorically to mean a line of thought or action which leads nowhere.

Cul-de-Sac is also the title of a 1966 film by Roman Polanski set on Lindisfarne and featuring Donald Pleasence and Lionel Stander.