Rabbi Isaac Luria Ashkenazi, known as Ari HaKadosh ("The Holy Lion") passed away on the 5th of Av of the year 5332 from creation (1572 CE). Born in Jerusalem in 1534, he spent many years in secluded study near Cairo, Egypt. In 1570 he settled in Sefad, where he lived for two years until his passing at age 38. During that brief period, the Ari revolutionized the study of Kabbalah, and came to be universally regarded as one of the most important figures in Jewish mysticism. It was he who proclaimed, "In these times, we are allowed and duty-bound to reveal this wisdom," opening the door to the integration of the teachings of Kabbalah--until then the province of a select few in each generation--into "mainstream" Judaism.

Links: A Tale of Two Kabbalists
Fallen Sparks
What is Kabbalah?
About The Ari