Ahaz (Hebrew: אָחָז, ʼĀḥāz ; "has held"; Greek: Ἄχαζ Akhaz; Latin: Ahaz; an abbreviation of Jehoahaz, "Yahweh has held") was king of Judah, and the son and successor of Jotham. He is one of the kings mentioned in the genealogy of Jesus in the Gospel of Matthew.

Ahaz was twenty when he became king of Judah and reigned for sixteen years. His reign commenced in the seventeenth year of the reign of Pekah of Israel.Edwin Thiele concluded that Ahaz was coregent with Jotham from 736/735 BC, and that his sole reign began in 732/731 and ended in 716/715 BC.William F. Albright has dated his reign to 735 – 715 BC.

His reign is described in 2 Kings 16; Isaiah 7-9; and 2 Chronicles 28. He is said to have given himself up to a life of wickedness, introducing many pagan and idolatrous customs (Isaiah 8:19; 38:8; 2 Kings 23:12). Perhaps his wickedest deed was sacrificing his own son, likely to have been Rimmon. He also added an idolatrous altar into the Temple. He ignored the remonstrances and warnings of the prophets Isaiah, Hosea, and Micah.