Rudolf Johannes Joseph Rainier von Habsburg-Lothringen, Archduke and Prince Imperial of Austria, Prince Royal of Hungary and Bohemia (8 January 1788 - 24 July 1831) was a Cardinal, an Archbishop of Olomouc, and a member of the House of Habsburg-Lorraine.
Born in Pisa, Italy, he was the youngest son of Emperor Leopold II and Maria Louisa of Spain. He was elected archbishop of Olomouc in 1819 and became cardinal in the year 1820.
In 1803 or 1804, Rudolf began taking lessons in piano and composition from Ludwig van Beethoven. The two became friends, and Rudolph became a supporter and patron of Beethoven; their meetings continued until 1824. Beethoven dedicated 14 compositions to Rudolph, including the Archduke Trio, the Hammerklavier Sonata, the Emperor Concerto and the Missa Solemnis. Rudolph, in turn, dedicated one of his own compositions to Beethoven. The letters Beethoven wrote to Rudolph are today kept at the Gesellschaft der Musikfreunde in Vienna.
On 24 March 1819 he was appointed, at the age of 31, Archbishop of Olomouc in the present day Czech Republic but then part of the Austrian Empire. He was made Cardinal-Priest of the titular church of S. Pietro in Montorio by Pope Pius VII on 4 June 1819. He was ordained a priest on 29 August 1819, and consecrated a bishop on 26 September.
In 1823 - 24, he was one of the 50 composers who composed a variation on a waltz by Anton Diabelli for Vaterländischer Kenstlerverein. In Rudolf's case, the music was published anonymously, as by "S.R.D" (standing for Serenissimus Rudolfus Dux).
