Muhammad ibn Rumahis (Arabic: محمد بن رماحس) was a Muslim Admiral in 10th Century Spain.
[1] He was born somewhere in the north of the Iberian Peninsula, where he was taken captive in a raid by the caliph Abd al-Rahman III (891-961).
[2] According to Abraham ibn Daud's Sefer HaQabbala, Ibn Rumahis captured a boat containing Shemariah ben Elhanan, Chushiel, father of Chananel ben Chushiel; Moses ben Hanoch; and one other anonymous rabbi while the four were traveling to raise money for the Talmudic academies in Babylonia.
This is attributed as the source of the spread of Jewish learning from Babylonia to Spain and North Africa.
Heinrich Graetz posited that the fourth captive was Nathan ben Isaac HaBabli, who settled, and was presumably sold, to the Jewish community in Narbonne.