Shams al-Din Ildeniz, Eldigüz or Shamseddin Eldeniz (Persian: اتابک شمس‌الدین ایلدگز, died c. 1175–1176) was an atabeg of the Seljuq empire and founder of the dynasty of Eldiguzids, atabegs of Azerbaijan, which held sway over Armenia, Iranian Azerbaijan, and most of northwestern Persia from the second half of the 12th century to the early decades of the 13th.

[1][2][3] His rise as the most powerful peripheral emirs of the Seljuq empire was aided by the necessity of having a large army against the frequent incursions from the neighboring Kingdom of Georgia.

His power in Azerbaijan grew stronger when Khass Beg ibn Palang-Eri was killed on the orders of sultan Muhammad II in 1153.

[8] Ildeniz then arranged a marriage between his son Pahlawan and the daughter of Inanch, amir of Rey, in order to secure the allegiance of this powerful dynasty.

Inanch marched against Hamadan, in order to place his brother Muhammad on the throne in 3 August 1161 but Arslan and Eldigüz defeated him in battle, forcing Ïnanch to flee.

A coalition of Muslim rulers - Shah-Armen Seyfettin Beytemür, Ahmadili Arslan-Aba, Arzen emir Fakhr ul-Din and Saltuk II, led by Ildeniz took the fortress of Gagi, laid waste as far as the region of Gagi and Gegharkunik, seized prisoners and booty, and then moved to Ani capturing and granting it to Shaddadid emir Shahanshah ibn Mahmud.

However, this time they were forestalled by George III, who marched into Arran at the beginning of 1166, occupied a region extending to Ganja, devastated the land and turn back with prisoners and booty.

Its governor Muayyad Ay-Aba submitted to Eldugiz since 1157, even captured Bistam and Damghan from Khwarazmshah and defeated Shah Ghazi Rustam.

By the time of his death around October–November 1175, Ildeniz was arguably the undisputed de facto master of many parts of the already fragmentized Great Seljuq Empire, centered on Iraq.