"Otto IV" beralih ke halaman ini. Untuk kegunaan lain, lihat Otto IV (disambiguasi).
Otto IV (1175 – 19 Mei 1218) adalah salah satu dari dua pesaing raja Jerman dari 1198, raja tunggal dari 1208, dan Kaisar Romawi Suci dari 1209 sampai ia terpaksa abdikasi pada 1215. Sebagai satu-satunya raja tunggal dari Wangsa Gwelf, ia memurkai Paus Innosensius III dan diekskomunikasi pada 1210.
Although Frederick II was crowned King of the Romans, King of Sicily, King of Jerusalem and Holy Roman Emperor, he was never crowned King of Italy at Pavia, Monza or Milan during his lifetime – see Sismondi's History of the Italian Republics in the Middle Ages, (1906), pg. 143; 147 and Kington-Oliphant's, History of Frederick the Second, Emperor of the Romans, Vol I, (1862), pg. 195 which specifically state that the Milanese refused to crown Frederick with the Iron Crown. Neither is his coronation as King of Italy mentioned in any modern source, such as Abulafia's, The New Cambridge Medieval History, Vol. V: c. 1198 – c. 1300, (1999)
Abulafia, David, The New Cambridge Medieval History, Vol. V: c. 1198 – c. 1300, Cambridge University Press, 1999
Bryce, James, The Holy Roman Empire, 1913
Comyn, Robert. History of the Western Empire, from its Restoration by Charlemagne to the Accession of Charles V, Vol. I. 1851
Dunham, S. A., A History of the Germanic Empire, Vol. I, 1835
Huffman, Joseph Patrick (2000). "Richard the Lionheart and Otto IV: Itinerant Kingship and the City of Cologne". The Social Politics of Medieval Diplomacy: Anglo-German Relations (1066–1307). University of Michigan Press. hlm.133–77.
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