Melatonin is a hormone naturally produced by the pineal gland in the brain, primarily responsible for regulating the sleep-wake cycle. It is commonly used as a supplement to treat sleep disorders such as insomnia and to alleviate jet lag by synchronizing the body’s internal clock with external cues. Melatonin production is influenced by light exposure, increasing in darkness to promote sleep and decreasing in light to encourage wakefulness. Beyond its role in sleep regulation, melatonin possesses antioxidant properties, supports immune function, and is involved in the modulation of mood and reproductive hormones. Available in various forms, including tablets, capsules, and liquids, melatonin supplements are widely used for their sleep-inducing effects and overall benefits to circadian rhythm management.