A bunk bed is a space-saving piece of furniture where one bed frame sits directly above another, connected by a ladder or stairs. The person sleeping on top climbs up to reach their mattress, while someone else sleeps on the lower bed underneath.

Bunk beds are common in children's bedrooms, summer camps, ships, military barracks, and anywhere people need to fit multiple sleepers into a limited space. Two kids sharing a bedroom might use bunk beds instead of having two separate beds taking up floor space, leaving more room for playing, studying, or storing their things.

The top bunk usually has railings along the side to prevent the sleeper from rolling off during the night. Many kids consider sleeping on the top bunk an adventure or special privilege, though some prefer the coziness and easier access of the bottom bunk. Bunk beds can also come in triple-decker versions, though these are less common.