Peter IV, called the Ceremonious (Catalan: el Cerimoniós), was from 1336 until his death the King of Aragon and also King of Sardinia and Corsica (as Peter I), King of Valencia (as Peter II), and Count of Barcelona (and the rest of the Principality of Catalonia as Peter III). In 1344, he deposed James III of Majorca and made himself King of Majorca.
His reign was occupied with attempts to strengthen the crown against the Union of Aragon and other such devices of the nobility, with their near constant revolts, and with foreign wars, in Sardinia, Sicily, the Mezzogiorno, Greece, and the Balearics. His wars in Greece made him Duke of Athens and Neopatria in 1381.
Upon succeeding his father he called a corts in Zaragoza for his coronation. He crowned himself, disappointing the Archbishop of Zaragoza and thus rejecting the surrender Peter II had made to the Papacy, in an otherwise traditional ceremony.
He conquered Sicily in 1377 but the possession was given to his son Martin.
In 1349, James invaded Majorca, but was soundly defeated by Peter's troops at the Battle of Llucmajor, in which he died. After James' death, Peter allowed James IV, his successor, to retain his royal title on purely formal terms until his death in 1375. After that date, Peter assumed the title. Majorca remained one of the component crowns of the Crown of Aragon until the Nova Planta decrees.
Peter died in Barcelona, aged 67.
There are no Sardinian kings named Peter with numbers 1 to 3. The Sardinian royal title did not have a specific line of succession and all Aragonese kings used their own primary titles.