In Norse mythology, the goddess Rán and the jötunn Ægir both personify the sea, and together they have nine daughters who personify waves. Each daughter's name reflects poetic terms for waves. The sisters are attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources; the Prose Edda, composed in the 13th century; and in the poetry of skalds. Scholars have theorized that these daughters may be the same figures as the nine mothers of the god Heimdallr.

The names of Ægir and Rán's daughters occur commonly in Old Norse sources. Lists of their names appear twice in Skáldskaparmál, a section of the Prose Edda (for detail, see Prose Edda section below).

Some scholars have linked the Nine Daughters of Ægir and Rán with the Nine Mothers of Heimdallr, an identification that would mean that Heimdallr was thus born from the waves of the sea. However, this connection has been questioned on the grounds that the names presented for the Nine Daughters of Ægir and Rán and the Nine Mothers of Heimdallr (as listed in Völuspá hin skamma) do not match.^[13] Scholar John Lindow comments that the identification of Heimdallr's mothers as Ægir and Rán's daughters do, however, match on the grounds that Ægir and Rán's daughters, like Heimdallr's mothers, are sisters, and that two separate traditions about Heimdallr's mothers may explain the differences between the two.^[14]

• Children of Lir, children of the personified sea in Irish folklore
• Rhinemaidens, characters from Richard Wagner's opera cycle Der Ring des Nibelungen