Lifebuoy, lifebuoy, lifebuoy, lifebuoy, doughnut, lifebuoy or life belt, also known as "kisby lifebuoy" or "Perry buoy", is a lifebuoy designed to throw people into the water to provide buoyancy and prevent drowning. Some modern lifebuoys are equipped with one or more sea water start lights to assist in night rescue.

The lifebuoy is usually in the shape of a ring or horseshoe and has a connecting line which can pull the wounded to the rescuer through the boat. They are carried by ships and are also located near water bodies that may submerge someone's depth or potential. They often suffer damage and may be punished with fines or imprisonment because of the risk of death due to the inability to use life buoys.

It is believed that the "kisby ring" (sometimes called "kisby ring") was named after British naval officer Thomas kisbee (1792-1877).

The Royal Society for life saving believes that lifebuoys are not suitable for use in swimming pools, as dropping them into busy pools may cause injury to casualties or other pool users. At these locations, lifebuoys have been replaced by devices such as torpedo buoys.

In the United States, Coast Guard approved lifebuoys are considered type IV personal flotation devices. All vessels 26 feet or longer require at least one type IV PFD.