A life jacket is a safety device intended to keep someone afloat in the event of them falling into a body of water, thus increasing their chances of rescue.

They can be made by enclosing foam cells in a synthetic shell, which is often made of nylon or polyester. Inflatable versions exist as well which are often folded up and kept in place by Velcro or zippers, or compacted into a belt pack. These styles are inflated by piercing a carbon dioxide canister that is connected to the device to inflate the bladder.

In the past, such devices were originally filled with either blocks of cork or kapok sealed in bags. These practices have been discontinued due to reliability and durability issues of said materials.