In Islam, "nafs" is an Arabic word that means "self", "psyche", "ego", or "soul". The term is used in the Quran in both the individualistic and collective sense, indicating that although humanity is united in possessing the positive qualities of a nafs, they are individually responsible for exercising the agencies of the "free will" that it provides them. The concept of nafs is important in the Islamic tradition, especially within Sufism and the discipline of gnosis (irfan) in Shia Islam.

There are different types or inclinations of the nafs based on evidence from the Quran and Sunnah, and scholars discuss these categories. The strength of each type depends on the degree to which a person indulges these inclinations. Those most indulged dominate and direct the actions and character of the individual, reflecting on the spiritual health of their heart. The different types of nafs include:

• Nafs al-Ammara Bissu: This is the inciting nafs, the commanding nafs, which has desires, appetite, and some people call it ego. It has anger, passion, lust, and all these things.

• Nafs al-Lawwama: This is the scolding nafs, the blaming nafs, the nafs of reproach. It is conscious of its own imperfections and often changes, remembers and forgets, submits and evades, loves and hates, rejoices and becomes sad, accepts and rejects, obeys and rebels.

• Nafs al-Mutmaʿinna: This is the tranquil nafs, the nafs at peace, which rests on the certitude of Allah.

Purification of the nafs involves subduing and controlling the first two types of nafs and polishing and strengthening the third type. When the angelic inclinations of the nafs are most dominant, they help bring the heart closer to Allah, constituting success for the believer.