Rav Yechezkel Levenstein (1895 - March 12, 1974), often referred to affectionately as Reb Chatzkel, was the mashgiach of the Mir Yeshiva before the war. There is scarcely a yeshiva today whose leaders have not been influenced to one degree or another, by the strong yet gentle character and the moving shmuessen of Reb Chatzkel who conveyed a faith in Hashem that was so pure and clear that it was virtually tangible. From prewar Europe and Eretz Yisroel, from Mir across Europe to the Far East, in postwar America and again in Eretz Yisroel, in Yerushalayim and Bnei Brak, Reb Chatzkel inspired three generations of bnei yeshiva with the faith to cling to Hashem and His Torah under all and any circumstances.
Reb Chatzkel's biography is available from Artscroll.