A dervish, darvesh, or darwīsh (from Persian: درویش, romanized: Darvīsh) is a Muslim who seeks salvation through ascetic practises and meditations. It can refer to an individual or to a member of a Sufi order (tariqah). Their focus is on the universal values of love and service, deserting the illusions of ego (nafs) to reach God. This is usually done by performing a life style which decreases bodily function to a minimum in order to attain what would be called "esoteric knowledge" in Western terminology. In most Sufi orders, a dervish is known to practice dhikr through physical exertions or religious practices to attain the ecstatic trance to reach God. Their most popular practice is Sama, which is associated with the 13th-century mystic Rumi.

For centuries, this was an individual practise, but in the 12th century, it began to be mostly practised in fraternities. The oldest historical fraternity is the Qadiriyya order, founded by Abdul Qadir Gilani. According to Islamic beliefs, each order derives their history from the Prophet Muhammad and are authorized by God (Allah) and taught by the angel Gabriel. The theology of such fraternities is always based on Sufism and can varyfrom quiteism to anti-nomianism. Those adhering to law are called ba-shar those who do not follow law are called bi-shar. In folklore dervishes are often credited with the ability to perform miracles and ascribed supernatural powers.

The actual etymology of the term is unknown. The Persian word darvīsh (درویش) may derive from the Middle Persian daryōs̲h̲, meaning poor or needy. The term has also been constructed from the composition of dar (door) and awiz (hanging), referring to someone who "hangs around doors" i.e. begs at the doors. However, the Middle Persian daryōs̲h̲ contradicts this.

These proposed meanings belong to folk-etymologies, meaning that the meaning of the term was ascribed after the term has been established. Furthermore, there is no essential connection between begging and a dervish, and it is also said that a "true dervish" would abstain from begging.

Given the obscure etymologies given in Persian dictionaries, it has been suggested that the term may be of Turco-Buddhist origin and derive from darni (Sanskrit) and arvis (Old-Turkish) referring to a "specialist in magic" as they are credited with magical abilities (i.e. healing, performance of miracles, protection spells, etc). Given that the term is mostly used in Central Asian, Turkish, and Persian culture, the meaning of a dervish may root in Turco-Buddhist beliefs, then transferred to Islam, where the meaning of the term was lost.

Dervishes try to approach God by virtues and individual experience, rather than by religious scholarship. Many dervishes are mendicant ascetics who have taken a vow of poverty, unlike mullahs. The main reason they beg is to learn humility, but dervishes are prohibited to beg for their own good. They have to give the collected money to other poor people. Others work in common professions; Egyptian Qadiriyya – known in Turkey as Kadiri – are fishermen, for example.

In a study on dervishes among Bedouins, reveals the process of initiation. It is believed that one does not choose to become a dervish, but is choosen by God. This happens by receiving barakah, which happens during a dream or a conscious encounter with an angel. Barakah is usually received after an encounter with evil forces, supposedly manifesting in a precedding proccess of mental suffering. After receiving divine blessing, the gift might be forfeited if the dervish betrays God.

Dervishes also work as exorcists and healers. They are believed to be able to detect the presence of evil spirits, such as jinn and devils, by means of divine gifts. The exorcism can include negotiations or confrontation with the spirit in a spiritual world.