Rabbi and liturgist of Cologne, of the twelfth century; a relative of the tosafist R. Eliezer b. Nathan; studied at Speyer under R. Isaac b. Elhanan, and at Mayence. He was one of the leaders of the "great synod" in which one hundred and fifty rabbis took part under the guidance of R. Jacob Tam and his brother Samuel (Rashbam). He is mentioned, and one of his responsa is cited, by Mordecai (Ket. 219; Shebu. 761; Ḳid. 515); another responsum is cited in "Or Zaro'a" (Shab. 45). Two of his piyyuṭim are extant: (1) for the second evening of the Feast of Tabernacles, a pizmon of seven stanzas, six verses in each; (2) "Reshut" to the "Hafṭarah," in Aramaic, consisting of thirty-two verses which rime in "raya." Both piyyuṭim give the acrostic of the author's name.