A duplex apartment, also known as a duplex or a maisonette, is a type of residential unit that consists of two separate living spaces connected by an internal staircase or a shared entrance. These units often occupy two floors within a larger building, such as an apartment complex, townhouse, or multi-family home.

Duplex apartments are popular among small families, individuals seeking additional space, or those who wish to generate rental income by leasing out one level while living in the other. They offer more privacy and space than traditional single-level apartments, but can be more expensive due to their size and additional features.