A penthouse is a luxurious apartment on the top floor of a tall building. The word comes from the idea of a structure built onto a roof, and today it describes the most expensive and desirable apartments in a building, often featuring large windows, private terraces, and spectacular views of the city below.

Penthouses became popular in the 1920s when wealthy people in cities like New York started converting rooftop spaces into elaborate living quarters. Before that, top floors were considered less desirable because people had to climb many stairs. But once elevators became common, the highest floors suddenly became the most sought after. Being up high meant fresher air, less street noise, and those amazing views.

A penthouse typically costs much more than other apartments in the same building. It might have its own private elevator entrance, multiple levels inside, or outdoor space where residents can enjoy being above the bustle of the city. In movies and books, penthouses often symbolize wealth and success, the kind of place where a successful business owner or famous artist might live.

The word can also refer to any structure built on a roof, like the small room that houses elevator machinery at the top of a skyscraper.