Mathematician and astronomer, born in Egypt. His father was a historian, biographer and scholar of hadith, who wrote two volumes about the history of Egypt. In Cairo, he worked as an astronomer for the Fatimid dynasty for 26 years, first for the Caliph al-Aziz and then for al-Hakim. He dedicated his most famous astronomical work, al-Zij al-Hakimi al-kabir, to the latter. This handbook of astronomical tables contained very accurate observations, many of which may have been obtained with very large astronomical instruments. Yunus was also an astrologer, predicting the date of his own death in seven days. The Ibn Yunus crater on the Moon is named after him.