The fourth son of emperor Karl I and empress Zita, Felix Habsburg-Lothringen died three weeks ago in San Angel, Mexico, media reports in Austria said, citing his death certificate.
His death follows that of his eldest brother and last heir to the Habsburg throne, Otto, just two months ago.
Born in 1916 in the Schönbrunn castle, two years before the fall of the Austro-Hungarian empire, Felix spent much of his childhood in exile in Switzerland, on the Portuguese island of Madeira, and in Spain, Belgium, France and the United States.
In 1952, Felix married Princess Anna-Eugenie von Arenberg, with whom he had seven children.
He will be buried in the Habsburg family vault in Muri, next to his wife.