A porch (from Old French porche, from Latin porticus ‘colonnade,’ from porta ‘passage’) is external to the walls of the main building proper, but may be enclosed by screen, latticework, broad windows, or other light frame walls extending from the main structure.

There are various styles of porches, all of which depend on the architectural tradition of its location. All porches will allow for sufficient space for a person to comfortably pause before entering or after exiting the building. However, they may be larger. Verandahs, for example, are usually quite large and may encompass the entire facade as well as the sides of a structure. At the other extreme, the Grand Hotel on Mackinac Island, Michigan has the longest porch in the world at 660 feet (200 m) in length.

In eastern North America and New England, a porch is a small area, usually unenclosed, that is at the main floor height usually used as a sitting area or for removal of working clothes so as not to get the interior of the house dirty, as the front door is accessed via the porch. In the Western United States, ranch style homes often use a covered porch to provide shade for the entrance and southern wall of the residence. In the Southern United States and Southern Ontario, Canada, a porch is often as broad as it is deep, and may provide sufficient space for residents to entertain guests or gather on special occasions. Older American homes, particularly those built during the era of Victorian Architecture, or the Queen Anne style, often included a porch in both the front and the back of the home. This is used as a sitting space as well. However, many American homes built since the 1940s with a porch only have a token one, (rear one) usually too small for comfortable social use and adding only to the visual impression of the building. The New Urbanism movement in architecture urges a reversal in this trend, recommending a large porch facing the street, to help build community ties.