Adolf Hitler died by suicide on April 30, 1945. He was just past his 56th birthday.
Hitler had, of course, realized for some time that the war was going badly. He planned to have Germany fight to the bitter end and to kill himself rather than to be captured. By late April of 1945, the Soviet Red Army had gotten to Berlin. On April 30th, there was heavy fighting in Berlin and the Red Army was within blocks of the bunker complex where Hitler had been living.
On that afternoon, Hitler and Eva Braun (whom he had officially married the day before) committed suicide. She took cyanide and he shot himself. Their bodies were then burned so that the Soviets could not abuse them for propaganda purposes.