Yahya ibn Idris ibn Umar (Arabic: يحيى بن إدريس بن عمر) was the ninth Idrisid ruler and sultan of Morocco. He took over after Yahya III in 904 and died in 917 when the Fatimids invaded Morocco.
Fatimid rule of Morocco continued for 8 years after the death of Yahya IV and the Idrisids only regained power after the rebellion of Al-Hasan ibn Muhammad. Al-Hasan's rule however was short lived and lasted for only about 3 years before the Fatimids ousted him. The Fatimids ruled for 10 more years only to be once again overthrown by the Idrisids under the leadership of Al Qasim Guennoun.