Rochus Misch, aged 96, died yesterday in Berlin after failing to recover from a heart attack, Michael Stehle, who owns the rights to a book written by Misch, told AFP.
Misch was among those who joined the Nazi leader in his bunker where Hitler eventually committed suicide days before Germany's surrender.
In a 2005 interview with AFP, Misch described how he had seen the Nazi leader and his wife Eva Braun dead in their bunker deep under the shattered city of Berlin.
Two days later, Misch, then aged 27, fled the bunker, where he had worked as a telephone operator, on May 2, 1945 as Soviet troops stormed the chancellery in Berlin.
More From This Section
He was taken prisoner by Soviet forces and held captive until 1953.
His 2008 book "The Last Witness" ("Der Letzte Zeuge") made it onto the bestseller list and brought Misch much attention.
An English translation is due to be published next month, Stehle said.
He told news site Spiegel online in 2007 that at his first meeting with the dictator, he had thought: "He wasn't a monster, he wasn't an Uebermensch, he stood opposite me like a perfectly normal gentleman, and spoke kind words.