A box office or ticket office is a place where tickets are sold to the public for admission to an event. Patrons may perform the transaction at a countertop, through a hole in a wall or window, or at a wicket. By extension, the term is frequently used, especially in the context of the film industry, as a metonym for the amount of business a particular production, such as a film or theatre show, receives. The term is also used to refer to a ticket office at an arena or a stadium.

Box office business can be measured in the terms of the number of tickets sold or the amount of money raised by ticket sales (revenue). The projection and analysis of these earnings is greatly important for the creative industries and often a source of interest for fans. This is predominant in the Hollywood movie industry.

To determine if a movie made a profit, it is not correct to directly compare the box office gross with the production budget, because the movie theater keeps nearly half of the gross on average. The split varies from movie to movie, and the percentage for the distributor is generally higher in early weeks. Usually the distributor gets a percentage of the revenue after first deducting a "house allowance" or "house nut". It is also common that the distributor gets either a percentage of the gross revenue, or a higher percentage of the revenue after deducting the nut, whichever is larger. The distributor's share of the box office gross is often referred to as the "distributor rentals", especially for box office reporting of older films.