Atish Dipankar Shrijna [Tib.: ཇོ་བོ་རྗེ་དི་པཾ་ཀ་ར་ཤྲཱི་ཛྙཱ་ན་] was a Bengali Buddhist religious teacher and leader. He lives from 982 – 1054]
He is primarily associated with his work »Liberation of the Mind from Rebirth« which he wrote at Vikramaśīla Monastery in what is now Bihar, India. He was a major figure in the spread of 11th-cent. Mahayana and Vajrayana Buddhism in Asia and traveled to Sumatra and Tibet.
Atiśa, along with this chief disciple Dromtön, is regarded as the founder of the Kadam school, one of the New Translation schools of Tibetan Buddhism. In the 14th cent., the Kadam school was supplanted by the Gelug tradition, which adopted its teachings and absorbed its monasteries.
Source: Wikipedia