Rābiʼa al-ʼAdawiyya al-Qaysiyya (Arabic: رابعة العدوية القيسية; c. 716 – 801 CE) or Rabia Basri was a poet, one of the earliest Sufi mystics and an influential religious figure from Iraq. She is regarded as one of the three preeminent Qalandars of the world.

Very little is known about the life of Rabi‘a, notes Rkia Elaroui Cornell.

What historical information can be ascertained from the earliest sources on Rabi‘a? As stated above, there is very little except to confirm that a Muslim woman ascetic and teacher named Rabi‘a al-‘Adawiyya or Rabi‘a al-Qaysiyya (the name ‘Adawiyya refers to her clan and the name Qaysiyya refers to her tribe) lived in or around the city of Basra in southern Iraq in the eighth century CE. [...] The commonly accepted birth date of 717 CE and death date of 801 CE come from a much later period and the ultimate source of these dates is unclear.

Cornell further notes that she was mentioned by two early Basran authors. "Because of this, they were familiar with her reputation. This local reputation is the best empirical evidence we have that Rabi‘a actually existed." She also writes, "To date, no written body of work has been linked conclusively to Rabi‘a al-‘Adawiyya."

Despite this, narratives about Rabiʿa grew over the centuries, and a considerable hagiography developed. Attar of Nishapur, a Sufi saint and poet who lived some four centuries later, recounted a now-famous story of her early life. Many of her hagiographies depict her using literary or philosophical tropes where she, like her Christian counterparts, embodied idealized religious individuals.

Often noted as having been the single most famous woman in Islam, Rabiʿa was renowned for her high virtue and piety. A devoted ascetic, when asked why she performed a thousand ritual prostrations both during the day and at night, she is said to have answered, "I desire no reward for it; I do it so that the Messenger of God, may God bless him and give him peace, will delight in it on the day of Resurrection and say to the prophets, 'Take note of what a woman of my community has accomplished.'"

Rabiʿa was described as being intense in her self-denial and devotion to God. Explaining her refusal to lift her head toward the heavens (towards God) as an act of modesty, she's noted as having said: "Were the world the possession of a single man, it would not make him rich ... because it is passing away."

According to Sufi accounts, she was the first to set forth the doctrine of divine love known as Ishq and is widely considered as being the most important of the early renunciants, a form of piety that would eventually be labelled Sufism.