Modafinil, sold under the brand name Provigil or Modalert among others, is a wakefulness-promoting medication used primarily to treat narcolepsy. Modafinil is also approved for stimulating wakefulness in people with sleep apnea and shift work sleep disorder. Modafinil is not approved by the US Food and Drug Administration (FDA) for use in people under age 17.

While modafinil is used as a cognitive enhancer or "smart drug" among healthy individuals seeking improved focus and productivity, its use outside medical supervision raises concerns regarding potential misuse or abuse. Research on the cognitive enhancement effects of modafinil in non-sleep-deprived individuals has yielded mixed results, with some studies suggesting modest improvements in attention and executive functions, while others show no significant benefits or even a decline in cognitive functions.

Modafinil has potential for causing severe allergic reactions, mental (psychiatric) effects, hypersensitivity, adverse interactions with prescription drugs, and misuse or abuse.