Abstract This article examines the nature of informal marriages using data from a 2018 survey of over ten thousand Facebook users in seven Muslim-majority countries: Algeria, Egypt, Iran, Pakistan, Palestine, Tunisia, and Turkey. The article explores current attitudes toward informal marriages as well as the nature of such unions among the predominantly Sunni and Shiʿi Muslim social-media users who took the survey. First, the article finds that informal marriages have diffused across the Sunni Muslim world. These marriages are not necessarily loveless unions between women of modest means looking for financial support and men seeking legitimate sexual partners. In fact, the survey suggests that women in such unions are less likely to be financially dependent on their partners. Informally married spouses are as likely to say that they love their partners as those who are formally wed. However, this love, whether in formal or informal marriages, does not necessarily entail a deep bond between partners who share their most intimate feelings. Marriage—whether formal or informal—is perceived as fragile, not a lifelong commitment. The rates of divorce in the countries surveyed are approaching those in the West. These informal marriages might therefore be thought of as a new form of cohabitation, a practice increasing throughout the world.