Fakhr al-Mulk Radwan (also Ridwan or Rudwan; died 10 December 1113) was a Seljuq ruler of Aleppo from 1095 to 1113.
He was the son of Tutush I and brother of Duqaq, but was raised by his tutor (atabeg) Janah ad-Dawla al-Husain. When Tutush died in 1096, Radwan inherited his Syrian possessions and ruled from Aleppo, though Janah ad-Dawla was in charge of actual governance. Duqaq soon revolted against his brother and took control of Damascus, throwing Syria into almost chaos and anarchy. Duqaq had the support of Yaghi-Siyan of Antioch, who had no quarrel with Radwan but disliked Janah ad-Dawla; joining Yaghi-Siyan and Duqaq was Ilghazi, governor of Jerusalem. Radwan allied with Ilghazi's brother Sökmen of Artukids.
Radwan attacked Yaghi-Siyan, and when Duqaq and Ilghazi came to assist him, Radwan besieged Damascus as well. However, Radwan soon quarreled with Janah ad-Dawla, who captured Homs from him, and with his atabeg out of the alliance, Yaghi-Siyan was much more willing to assist him. This new alliance was sealed with a marriage between Radwan and Yaghi-Siyan's daughter. The two were about to attack Shaizar when they heard of the arrival of the First Crusade; all the various alliances were disbanded and everyone returned to their own cities, though if any of the alliances had remained intact, or they had all worked together, they would likely have been able to prevent the success of the crusade.
In 1103 Janah ad-Dawla was murdered by an Assassin named al-Hakim al-Munajjim, one of the members of the entourage of Radwan. This was the first appearance of the Assassins in Syria. Upon Duqaq's death in 1104, two weak rulers followed him in Damascus and Radwan probably captured the city the same year. The throne remained in Aleppo, however. In 1105 he assisted in the defense of Tripoli, which was being attacked by the crusaders. That same year, Tancred, Prince of Galilee, regent of the Principality of Antioch, defeated him in the Battle of Artah and briefly threatened Aleppo itself. Radwan and Tancred frequently came into conflict, until Tancred reduced Aleppo to a tributary state in 1111. The qadi of Aleppo, Ibn al-Khashshab, travelled to Baghdad to meet with the Abbasid caliph when Radwan was unwilling to pursue war with Tancred. Ibn al-Khashshab succeeded in having Mawdud of Mosul sent to Aleppo's aid, but Radwan was also antagonistic to his Muslim neighbours, even when they tried to help him against the crusaders; Mawdud was soon murdered by the Hashshashin, possibly with Radwan's approval.