Ilyas ibn Mudar (Arabic: إلياس بن مضر) also spelled al-Yas was a pre-Islamic Arabian tribal chief and an ancestor of the Islamic prophet Muhammad.

A pioneer of pre-Islamic monotheism, Ilyas ibn Mudar lead a period of religious reform during his rule over the Hijaz to eradicate the worship of idols.

[9] Ilyas ibn Mudar followed a monotheistic form of religion that was incompatible with the pre-Islamic Arabian polytheism.

As such, he openly denounced idol worship to the mixed reactions of his people, who would eventually accept his opinion and follow him in rejecting polytheism.

[7] Ilyas' grandson, Khuzayma ibn Mudrika would be the first to set up the idol of Hubal which the Arabs worshipped for generations until the rise of Islam in the 7th century CE.