Charter of Duke Trpimir (), also known as Trpimir's deed of donation () is the oldest preserved document of the Croatian law, the oldest from the court of one of the Croatian rulers and the first national document which mentions the Croatian name. Charter, dated to 4 March 852, is not preserved in its original form but in five subsequent transcripts out of which the oldest is from year 1568.
Dating
Dating of the Charter is contained in the following sentence in Latin: Regnante in Italia piissimo Lothario Francorum rege per indictionem XV sub die IIII Nonis Martii ().
Historians Daniele Farlati and Ivan Kukuljević Sakcinski considered that the indiction XV refers to the year 837, while Ivan Lučić Lucius considered that indiction refers to the year 838, which cannot be because of indiction. Historian Franjo Rački corrected the opinion of Farlati and Kukuljević Sakcinski because Lothair I reigned as "Francorum rex", King of Franks, only since year 840, and also because, according to chronicler John the Deacon, Duke Mislav reigned over Duchy of Croatia in year 837. Accordingly, indiction XV can only refer to year 852.
Miho Barada gave the first extensive palaeographic-diplomatic analysis to attempt to reconstruct the original text. In addition, valuable contributions were also given by Lovre Katić and Marko Kostrenčić. Držislav Švob considered this Charter to be forgery from 14th century because of its "unconvincing arguments and arbitrary assumptions".
In recent years, the debate on the issue was renewed by Lujo Margetić who thought that, because Lothari had already left Italy in year 840 and succeeded his father to the imperial throne, it is very unlikely that Trpimir was unaware of that change on the imperial throne even twelve years later. According to Margetić, the real date when the document was written would be March 4, 840. This Margetić's claim is supported by writings of John the Deacon according to which Justin was Archbishop of Split in year 840 after Archbishop Petar which is mentioned in the Charter.
Content
Although the Charter is preserved in fragments it can be seen that the ruler (Dux Chroatorum) had almost unlimited power in the country, because Trpimir called himself "the ruler of the Croats by the grace of God". Charter proves the existence of Croats before Trpimir, because it confirms deed of donation given to the Archdiocese of Split by Trpimir's predecessor Mislav. In addition, Trpimir gave Church of St. George in Putalj and some other estates with associated serfs to the Archdiocese of Split. Charther shows that Croatia was a feudal state in formation and that the Croatian ruler had his state government which was made out of his courtiers and military and administrative officials, such as prefects and court chaplains. Trpimir also established the right of the Catholic Church to collect tithe. Feudal nature of the ruler's authority is confirmed by the fact that Trpimir had national territory and his own feudal domains. Although Trpimir acted as a real ruler, he was not formally independent, but was rather a vassal of the Successor of Frankish ruler in Italy, Lombardy king Lothair. On the basis of this Charter, it can be concluded that the Croatian state finally emerged in the third decade of the 9th century.