In Norse mythology, the Nine Mothers of Heimdallr are nine sisters who gave birth to the god Heimdallr. The Nine Mothers of Heimdallr are attested in the Prose Edda, written in the 13th century by Snorri Sturluson; in the poetry of skalds; and possibly also in a poem in the Poetic Edda, a book of poetry compiled in the 13th century from earlier traditional material. Scholars have debated what being "born of nine mothers" implies and have sought to connect the notion to other European folk motifs. Scholars have theorized that Heimdallr's Nine Mothers may be identical to the Nine Daughters of Ægir and Rán, who personify waves. In turn, Heimdallr would be born of the sea.