Atiśa (c.980-1055). The short name of Atiśa Dīpaṃkāra Śrījñāna. Born in Bengal into a royal family, he was a renowned Buddhist scholar and monk who later became one of the leading teachers at the university monastery of Vikramaśīla. He was invited to Tibet in 1043, where he stayed until his death, to assist in the re-establishment of Buddhism. He was especially devoted to systematizing the Buddhist teachings available in Tibet into a structured path, as is reflected in his main work, the Lamp for the Path to Enlightenment (Bodhi-patha-pradīpa). He founded the Kadampa school with his chief Tibetan disciple, Dromtön, and thus effected a lasting influence upon the nature of Tibetan Buddhism.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)