Boann or Boand (modern spelling: Bóinn) is the Irish mythology goddess of the River Boyne, a river in Leinster, Ireland. According to the Lebor Gabála Érenn she was the daughter of Delbáeth, son of Elada, of the Tuatha Dé Danann. Her husband is variously Nechtan, Elcmar or Nuada. Her lover is the Dagda, by whom she had her son, Aengus. In order to hide their affair, the Dagda made the sun stand still for nine months; therefore, Aengus was conceived, gestated and born in one day.
As told in the metrical Dindshenchas, Boann created the River Boyne. Though forbidden to by her husband, Nechtan, Boann approached the magical well of Segais (also known as the Well of Wisdom), which was surrounded by hazel trees. Nuts from the hazels were known to fall into the well, where they were eaten by the speckled salmon (who, along with hazel nuts, also embody and represent wisdom in Irish myth). Boann challenged the power of the well by walking around it counter-clockwise; this caused the waters to surge up violently and rush down to the sea, creating the River Boyne. In this catastrophe, she was swept along in the rushing waters, and lost an arm, leg and eye, and ultimately her life, in the flood. The poem equates her with famous rivers in other countries, including the Severn, Tiber, Jordan, Tigris and Euphrates.
She also appears in Táin Bó Fraích as the maternal aunt and protector of the mortal Fróech.
Her name is interpreted as "white cow" (Irish bó fhionn; Old Irish bó find) in the dinsenchas. Ptolemy's 2nd century Geographia shows that in antiquity the river's name was Bubindas, which may derive from Proto-Celtic *Bou-vindā, "white cow".
Modern-day commentators and Neopagans sometimes identify Boann with the goddess Brigid, or believe Boann to be Brigid's mother; however there are no Celtic sources that describe her as such. It is also speculated by some modern writers that, as the more well-known goddess, and later saint, the legends of numerous "minor" goddesses with similar associations may have over time been incorporated into the symbology, worship and tales of Brigid