Branimir (Latin: Branimirus) was Duke of Croatia, reigning from 879 to c. 892. His country received papal recognition as a state from Pope John VIII on 7 June 879. During his reign, Duchy of Croatia retained its sovereignty from both Carolingian and Byzantine rule and became de jure independent. His rule marks the first real peak of early medieval Croatia. It was characterized by establishing closer relations with the Holy See, ecclestical re-organization in the former Roman province of Dalmatia, Christianization, and (re)construction of churches. Branimir is mentioned, for the period, in many reliable primary and secondary written and epigraphic sources.

In 879, a "certain Slav of the name Branimir" reportedly had the weak Duke Zdeslav, a supporter of the Byzantine Empire, killed near Knin in a rebellion that he led, per John the Deacon's Chronicon Venetum et Gradense (early 11th century).

Five papal letters sent between 879 and 882 are preserved in the Epistolae Ioannis VIII. During the solemn divine service in St. Peter's church in Rome in 879, Pope John VIII gave his blessing to the duke, the duke's authority and the whole Croatian people and country, about which he informed Branimir in the first letter. The Pope brought this decision on 21 May 879, and confirmed it in his letter on 7 June 879 (mentioning him as Dilecto filio Branimir). As the blessing was reported by the Pope himself twenty days later, it may have had a significant meaning for the time, recognizing Croatia as a relevant part of medieval Christian Europe as well as a sovereign state. In the third letter of the same month, Branimir is once again mentioned (as principis ... Branimir), and the letter is titled to all honorable priests and all the people (Omnibus uenerauilibus/sacerdotibus et uniuerso populo).

After 880, Branimir did not succumb to the pressure of the Carolingian Emperor Charles the Fat to recognize his sovereignty, even after the emperor entered into an alliance with the Republic of Venice against Croatia. In Branimir's time, Venetians had to pay taxes to Croatia and to the Narentines for the right to travel by ship along the eastern Adriatic coast, while the Dalmatian cities under Byzantium protection paid 710 ducats of tribute to the Croatian ruler.

Throughout his reign, Duke Branimir worked on increasing the duchy's independence. According to the map of his contemporary, Anglo-Saxon king Alfred the Great (871–899), the territory of "Dalmatia" was between the Adriatic Sea, Danube, "desolate lands", Bulgars and Achaia. Branimir reigned until around 892. He was succeeded by Trpimir I's third son, Muncimir.

At the time pope's commitment with Branimir is obvious intention to connect Croatian Church with the Holy See and Diocese of Rome, but also affirm old organization in the province of Dalmatia in which ancient Salona (then Split) was the metropolitan centre of Dalmatia. In 880-882, Duke Branimir via Theodosius, the bishop of the Diocese of Nona (episcopus Croatorum) which was formed on initiation of Patriarchate of Aquileia, wrote to Pope John VIII affirming commitment to the Roman Papacy, and recognized the supreme ecclesiastical authority of the bishop of Rome.

However, the situation complicated until 887 during the time of pope Stephen V (information is found in few letters and preserved in Decretum Ivonis and Decretum Gratiani Collectio Britannica). The previous archbishop of Split, Marin, died and Theodosius was promoted to the position by Aquileian patriarch Walpert in 886, but did not abolish Diocese in Nin as wanted by the Holy See, however, eventually in 887–888 was confirmed as the archbishop of Split (with a pallium). Later after his death, Diocese of Nona once again will be temporary separated from the Archdiocese of Split.

Under the influence of Methodius' baptising missions in 882 who made a stop in Croatia on his way from Moravia to Constantinople, Branimir possibly also endorsed parallel usage of Latin and Slavic in liturgy.