A spinster (or old maid) is a woman who has never been married, though it is usually applied only to women who are regarded as beyond the normal age for marriage. The word spinster came into common use during the early 19th century when the task of spinning cloth had been pushed onto unmarried women as a way to earn their keep in the home.

There used to be quite a stigma related to being a spinster, but this onus has somewhat disappeared in modern Western Civilization. The term is also of legal use in some places; in the United Kingdom, for instance, until the introduction of the Civil Partnership Act 2005 any woman never previously married was categorised as a "spinster" on a marriage licence, regardless of her age at the time the licence was issued (with a never-married man being listed thereon as a "bachelor").

In Australia parties are held for young single people to meet and socialise (particularly in the rural areas), these events are known as Bachelor and Spinster Balls or colloquially 'B and S Balls'.