A soulmate is a person with whom one feels a deep or natural affinity. This connection is often associated with love, romance, intimacy, sexuality, spirituality, or compatibility, and may also involve trust and comfort. In social science, a model titled the "soulmate model" exists. It is defined as relationships where one perfect person is designed to complete the subject romantically.

In contemporary usage, the term soulmate typically refers to a romantic or platonic partner with whom one shares a particularly strong bond. It is frequently used to suggest the closest relationship a person can have, and is sometimes understood as an exclusive or lifelong connection. Believers in the concept often describe soulmates as individuals who make each other feel “complete,” reflecting the idea that two souls are destined to unite.

The earliest recorded use of the term soulmate in English appears in a letter by Samuel Taylor Coleridge dated 1822.

In rabbinic and mystical literature, the concept of bashert (Yiddish: “destined one”) conveys the idea of a divinely ordained partner. The Talmud (Sotah 2a) states that “forty days before the formation of a child, a heavenly voice proclaims whose daughter he will marry.” Kabbalistic writings elaborate that a soul is divided before birth into male and female halves, which are reunited in marriage. The Baal Shem Tov is quoted as saying: “From every human being there rises a light that reaches straight to heaven, and when two souls destined to be together meet, the streams of light join and a brighter light goes forth from the united being.”

In Jewish folklore and later Kabbalistic writings, Adam is sometimes described as having had a first wife, Lilith, who was created from the same dust as him. According to this tradition, Lilith left Adam after refusing to submit to him, insisting instead on equality derived from their identical origin. In contrast, Eve is portrayed as Adam’s destined companion. Some rabbinic commentaries hold that her creation from Adam’s body symbolized an indissoluble union, with one interpretation suggesting that Adam was originally a dual-faced being divided at her creation.

A midrashic tradition states that in early generations, each male child was born with a twin sister destined to be his spouse. This belief extended to Cain and Abel, and later to Jacob and Esau, whose companions were identified in some commentaries with Rachel and Leah.

A lesser-known folktale concerns King Solomon, who, fearing that one of his daughters was destined to marry a poor man, secluded her in a tower deep within a forest. In the story, a bird of prey delivers her fated partner to the tower, where the two fall in love. The tale concludes with Solomon recognizing the young man’s scholarly virtues despite his lack of wealth, thereby fulfilling the destined match.

In Plato’s Symposium, the comic playwright Aristophanes presents a myth to explain the origin of love. According to his account, humans were originally androgynous beings with four arms, four legs, and a single head with two faces. Fearing their power, Zeus split them in half, condemning each to spend their lives searching for its missing counterpart (the term used by Plato is τὸ ἕτερον ἥμισυ, tó héteros ímisy, lit. "the other half"). Aristophanes describes this longing for unity as the source of human desire, stating that “love calls back the halves of our original nature together; it tries to make one out of two and heal the wound of human nature.”