Abu Nasr Shams al-Muluk Duqaq (probably died in 1104) was the Seljuk ruler of Damascus from 1095 to 1104. He inherited Damascus and Syria from his father, Tutush I, but Duqaq's older brother Radwan revolted and the realm was split, with Radwan ruling northern Syria from Aleppo. Duqaq was succeeded by Tutush II as the ruler of Damascus.
Duqaq was a son of the Seljuk ruler of Syria, Tutush I, and Khatun Safwat al-Mulk, He was the brother of Radwan.
Duqaq later joined Kerbogha of Mosul to attack the crusaders after they had occupied Antioch in June of 1098, but during the battle, Duqaq's line deserted and Kerbogha was defeated.
Meanwhile, Bohemund and Robert were attacked by an army under Duqaq of Damascus, which had marched north to come to Antioch's aid.
Like Duqaq before him, he too was defeated, at Harim outside Antioch, on February 9.
The crusaders were luckily granted time to prepare for their arrival, as Kerbogha had first made a three-week long excursion to Edessa, which he was unable to recapture from Baldwin of Boulogne, who had taken it earlier in 1098.