A townhouse, townhome, town house, or town home is a type of terraced housing. A modern townhouse is often one with multiple floors on a small footprint. In older British usage, the term originally referred to any type of city residence (normally in London) of someone whose main or largest residence was a country house.

Historically, a townhouse was the city residence of a noble or wealthy family, who would own one or more country houses in which they lived for much of the year. From the 18th century, landowners and their servants would move to a townhouse during the social season (when major balls took place).

In the United States and Canada, a townhouse has two connotations. The older predates the automobile and denotes a house on a small footprint in a city, which because of its multiple floors (sometimes six or more) has a large living space, often with servants' quarters. The small footprint of the townhouse allows it to be within walking or mass-transit distance of business and industrial areas of the city, yet luxurious enough for wealthy residents of the city.

Townhouses are expensive where detached single-family houses are uncommon, such as in New York City, Philadelphia, Montreal, and San Francisco. A brownstone townhouse is a particular variety found in New York.

Rowhouses are similar and consist of several adjacent, uniform units. Originally they were located in older, pre-automobile urban areas such as Baltimore, Philadelphia, and New Orleans; however, they are now found in lower-cost suburban housing developments as well. A rowhouse typically has a continuous roof and foundation with a single wall dividing adjacent townhouses, but some have a double wall with inches-wide air space in between the units, which share a common foundation. A rowhouse will generally be smaller and less luxurious than a dwelling called a townhouse.

Over time the term townhouse has come to be used to describe non-uniform living units that are designed to mimic a detached home. The distinction between living units called apartments and those called townhouses is that a townhouse usually consists of multiple floors and has its own outside door as opposed to being on only one floor and/or having access via either an interior hallway or an exterior balcony-style walkway. Another distinction is that in most areas of the United States outside of the very largest cities, apartment refers to rental housing, while townhouse typically refers to an individually owned dwelling, with no other unit beneath or above. However, the term townhouse-style apartment is sometimes used for bi-level rental apartments.

Townhouses can also be "stacked". Such homes have multiple units vertically (typically two), normally each with its own private entrance from the street or at least from the outside. They can be side by side in a row of three or more, in which case they are sometimes referred to as rowhouses. A townhouse in a group of two could be referred to as a townhouse, but in Canada and the United States, it is typically called a semi-detached home, a duplex, or in some areas of western Canada, a half-duplex.

In Canada, single-family dwellings of any type (e.g., detached homes, apartments, mobile homes, or townhouses) are split into two categories of ownership: