A lounger or lounger (chamastro in Mexico)[1]​[2]​ is a pool, garden or beach piece of furniture, often made up of sheets of white plastic that is designed for people to lie down on or sit on while relaxing.

With a bed-like structure, the top of the surface can be reclined to allow the user to sit up and read or kept completely flat to allow resting or tanning in a horizontal position. It may have side arms or simply consist of a horizontal body with legs. Sun loungers are often combined with a mat that is tied to their structure to make resting more comfortable. The configuration of its legs makes it a stackable piece of furniture, which reduces the space occupied when carrying out maintenance or cleaning tasks on the facilities.

On some beaches and hotels, sun loungers are made available to the user, sometimes on a rental basis that allows them to be used throughout the day.