Mahmoud al-Zahar (Arabic: محمود الزهار‎) (born 1945) is a co-founder of Hamas and a member of the Hamas leadership in the Gaza Strip. Since the formation of the Hamas/"Change and Reform" government in the Palestinian National Authority in March 2006, al-Zahar has served as foreign minister in the government of prime minister Ismail Haniyeh. Prior to that he was seen as a major candidate among the Hamas members elected to the Palestinian Legislative Council for prime minister, as he was at that time the most senior official within the organization. In the end the party decided to go with the then-unknown Haniyeh because al-Zahar is considered the leader of the movement's radical wing. al-Zahar's son, a member of the Hamas military wing, the Izz ad-Din al-Qassam Brigades, was killed in an Israeli raid in Gaza on January 5, 2008.

Little is known about al-Zahar's early life beyond the report that he was born to a Palestinian father and an Egyptian mother.

At the age of 26, he graduated from the Cairo University Faculty of Medicine and five years later he got his Masters Degree in General Surgery from Ain Shams University, Cairo. He then became the adviser to the Palestinian Health Minister, and helped create the Palestinian Medical Society and was one of the primary founders of the Islamic University in Gaza in 1978.