A closet (especially in North American usage) is a small and enclosed space, a cabinet, or a cupboard in a house or building used for general storage or hanging clothes. A closet for food storage is usually referred to as a pantry. A closet, through French from Latin clausum, "closed" began life in the 17th century as a small private room, often behind a bedroom, to which a man or woman could retire, for privacy, reading, or enjoyment of personal works of art: for this usage, see Cabinet (room).

Modern closets can be built into the walls of the house during construction so that they take up no apparent space in the bedroom, or they can be a large, free-standing piece of furniture designed for clothing storage, in which case they are often called a wardrobe or armoire. Closets are often built under stairs, thereby using awkward space that would otherwise go unused.

In current British usage, a "wardrobe" can also be built-in, and the word "cupboard" can be used to refer to a closet. In Elizabethan and Middle English, closet referred to a larger room in which a person could sit and read in private, but now refers to a small room in general. In Indian usage, a closet often refers to a toilet. This probably originated from the word water closet, which refers to a flush toilet.

In North America, chests, trunks and wall-mounted pegs typically provided storage prior to World War II. Built-in wall closets were uncommon and where they did exist, they tended to be small and shallow. Following World War II, however, deeper, more generously sized closets were introduced to new housing designs, which proved to be very attractive to buyers. It has even been suggested that the closet was a major factor in peoples' migration to the suburbs.