Ahmad Sanjar was the Sultan of the Seljuq Empire reigning from 1118 until 1157. He was the longest-reigning Muslim ruler until the arrival of the Mongol Empire, as well as the last ruler of the Seljuk Empire.
In 1096, he was given the province of Khorasan to govern under his brother Muhammad I. Over the next several years Ahmed Sanjar became the ruler of most of Iran (Persia) with his capital at Nishapur. A number of rulers revolted against him and continued the split of the Great Seljuq Empire that had started upon dynastic wars. In 1107, he invaded the domains of the Ghurid ruler Izz al-Din Husayn and captured him, but later released him in return for tribute.
Sanjar died on 8th May 1157 and was buried at Merv. His death ended the Seljuk Empire, which fragmented into smaller states as the Seljuks were relegated to controlling just Iraq and Azerbaijan.
Ahmad Sanjar featured on the front of the 5 Turkmenistan Manat banknote.
Image Source: Wikipedia.org