The Narentines were a South Slavic tribe noted as pirates on the Adriatic Sea in the 9th and 10th centuries. They occupied an area of southern Dalmatia centered at the river Neretva (Narenta). Named Narentani in Venetian sources, they were called Paganoi, "pagans", by the Greeks, as they were still pagan after the Christianization of the neighbouring tribes. They were fierce enemies of the Republic of Venice, attacking Venetian merchants and clergy traveling through the Adriatic, and even raiding close to Venice itself and defeating the doge several times. Venetian–Narentine peace treaties did not last long, as the Narentines quickly returned to piracy. They were finally defeated in a Venetian crackdown at the turn of the 10th century and disappeared from sources by the 11th century.

The word Narentine is a demonym derived from the local Neretva River (Latin: Narenta). The terms "Narentines", "Pagania" or "Pagans" are found in two contemporary sources: De Administrando Imperio (DAI), a mid-10th century Greek work, and Chronicon Venetum et Gradense, a Venetian chronicle by John the Deacon from the early 11th century. In De Administrando Imperio of Byzantine Emperor Constantine VII Porphyrogenitus (r. 913–959), the tribe is called Paganoi (Greek: Παγανοὶ, Παγανοἰ), and their polity Pagania (Παγανὶα, Παγανἰα), in Greek, while also noting that in Latin they are called Arentanoi (Αρεντανοἰ) and their polity Arenta (Αρεντα). Chronicler John the Deacon used the geographical term Narentani (as in princeps Narentanorum, Narrentanos Sclavos). In Serbo-Croatian, the tribal name is rendered as Neretljani (Неретљани), Neretvani and Pagani (Пагани), while the polity mostly as Paganija (Паганија).

In DAI's chapters Story of the province of Dalmatia and Of the Pagani, also called Arentani, and of the country they now dwell in, the geography of Pagania is described. Pagania had the counties (župa (zoupanias)) of Rhastotza, Mokros and Dalen. Rhastotza and Mokros lay by the coast, and had galleys, while Dalen was distant from the sea and was based on agriculture. Pagania had the inhabited cities of Mokron (Makarska), Beroullia (presumably Brela), Ostrok (Zaostrog) and Slavinetza (near Gradac), and the large islands of Kourkra/Kiker with a city (Korčula), Meleta/Malozeatai (Mljet), Phara (Hvar) and Bratzis (Brač). The Pagani raised flocks on the islands. Islands in the vicinity but not part of Pagania were Chora (presumably Sušac), Iës (Vis) and Lastobon (Lastovo). Croatia was situated to the northwest, and Zachumlia to the east; Serbia was situated inland to the northeast, behind Pagania, Zachumlia, Travunia and Dioklea, and bordered to Croatia on the Tzentina (Cetina) River.

The Sclaveni (South Slavs) overwhelmed the Balkans in the 6th century. In 639 AD, Narona, until then a flourishing Roman city, was destroyed by a horde of Avars and Slavs. A few years later, Slavic tribes took control of the lower Neretva. The Slavs built a new town on the ruins of Narona, and erected a monument to their Slavic god Svetovid, on the ruins of Roman temples. According to Evans, Narentia became a stronghold for pagans in the Balkans, similarly to Balto-Slavs in Rügen (at Jaromarsburg). In 642, Slavs invaded southern Italy and attacked Siponto, by ship from the Dalmatian coast. Slavic naval raids on the Adriatic increased and it became unsafe for travel.

The first conflicts between the Venetians and Narentines came immediately before 830, around which time the first peace agreement was signed between the two (the Venetian Doge and Sclavorum de insula Narrentis). Narentine Slavs sent envoys to Doge Giovanni I Participazio (r. 829–836). P. Skok believes this period also being the first contact between Venice and the middle Dalmatian islands. According to Šafárik (1795–1861), by the beginning of the 9th century their power had increased so much that Doge Giovanni I attacked them and then offered them peace. The Republic of Venice was de facto subordinate the Byzantine Empire, a period in which Venice expanded its trade relations towards the East. In the first half of the 9th century Byzantium was struck by internal unrest, while the Bulgars and Arabs strengthened themselves thanks to this. Arabs took Crete in 825, Palermo in 831, Taranto in 839, then after destroying the Venetian navy by 840, they roamed freely in the Adriatic. In 841 Arabic ships attacked Adriatic cities and reached a confluence of the Padua river, while smaller contingents attacked Budva, Roza and Lower Kotor. In 842 the Arabs conquered Bari, and in 846 reached Rome itself. The Venetian navy, obliged to defend the Byzantine Adriatic, were occupied almost fully with battles with the Arabs. The Byzantine navy rarely appeared, and with small numbers of ships. This, and Arab harassment, gave the Slavic pirates around the Neretva upswing to develop their ship capabilities. When the Venetian navy was in Sicilian waters as guards in 827–828, the Narentines received momentum; when the Venetian navy returned, they calmed down. Venetian chronicles speak of a Narentine leader having been baptized in Venice, for greater security for the latter; however, the Narentines are unsteady and deceptive as their sea; as soon as events in Venice or the Adriatic worsen, the Narentines continued their piracy. One of their attacks in 834–835, when they robbed and killed some Venetian merchants returning from Benevento, caused great resentment against them in Venice.

In order to stop these assaults, the Venetians undertook a large expedition against the Dalmatian Slavic pirates in 839. Doge Pietro Tradonico sent warships against the Slavic lands (Sclavenia). According to F. Šišić Doge Pietro ordered an attack on the Narentines in the spring of 839. According to V. Klaić, Tradonico had first defeated and made peace with the Croats under Mislav, then proceeded to attack the Narentine islands and make peace with Narentine leader Drosaico. There are no information on the fights that year, but it is known that peace was concluded with Croats and a part of the Narentines. Venetian chronicler John the Deacon (1008) records a renewal of the peace treaty signed by Drosaico (ad Narrentanas insulas cum Drosaico, Marianorum iudice, similiter fedus instituit). The peace with the Narentines did not last long, perhaps as the Narentines signed it to avoid danger, or more likely because it was not concluded with all, but a tribe or clan of the Narentines. In 840 the Venetians attacked Narentine leader Ljudislav, ending in failure; Ljudislav (Liuditus sclavus), possibly a successor or co-ruler of Drosaico, defeated the Venetian Doge and killed hundreds of his men. According to Klaić it was the Narentines who broke the peace. It seems that Narentine piracy even reached Istria by February 840. The 840 Venetian–Frankish treaty included common fight against Slavic tribes (generationes Sclavorum inimicas). After two defeats to the Venetian navy by the Arabs immediately after, the Venetians were unable to enter new fights with the Dalmatian Slavs. In 846 the Narentines reached close to Venice itself, and raided nearby Caorle.

The arrival of Basil I (r. 867–886) to the Byzantine throne led to important changes in Byzantium; energetic, he managed to enter closer ties with the Bulgarians, and even the distant Croats, and protected the Empire well. When Ragusa (Dubrovnik) asked for the emperor's help against the threat of the Saracens, he dispatched a strong navy into the Adriatic. Byzantine admiral Niketas Ooryphas took up closer contacts with the Slavic tribes around Ragusa, the Zachumlians, Travunians and Kanalites, and invited them to jointly combat the Saracens, both on land and sea, in 869. Only Slavic tribes of southern Dalmatia were called to cooperate; to the north, the Croats and Dalmatians entered relations with Italian king Louis at the dismay of the Byzantines. When some "Slavs" (Narentines according to Narayan) in March 870 kidnapped the Bishop of Rome's emissaries returning home from the Fourth Council in Constantinople, the Byzantines used this as a good pretext to attack and force them into submission (871). The DAI mentions that the Narentines were called "pagans, because they did not accept baptism in the time when all Serbs were baptized", which is placed during Basil's rule. The Narentines are not mentioned in relation to the Byzantine military expedition on Bari dispatched by Basil I (r. 867–886), in which other Dalmatian Slavs participated. The Croats, Serbs, Zachlumians, Travunians, Konavlians, Ragusans, "with all the men of the towns of Dalmatia", crossed over the sea to Langobardia and took Bari. Basil returned Dalmatia under Byzantine rule by 878, and a large part of Dalmatia was put under the Patriarchate of Constantinople. The DAI claims that the Dalmatian Slavs asked Basil I to baptize them; the Christianization of the Narentines seems to have failed. According to Evans, the Narentines remained pagan until 873, when Byzantine admiral Ooryphas persuaded them to accept baptism. While Doge Orso I Participazio and his son Giovanni II Participazio made peace and an alliance with the Croats after 876, the Venetians were still at war with the Narentines.

In 880 the Venetian–Frankish treaty was renewed. In 887 Doge Pietro I Candiano sent troops against the Narentine Slavs, landing at the "Slavic Hill" (mons Sclavorum), putting the Slavs to flight. The Narentines were defeated in a battle in August 887 at Makarska, and their five ships were destroyed with axes. With help from neighbours, the Narentines decisively defeated the Venetian navy on 18 September 887, with the Doge killed in action and his body left laying (Andrea Tribun later secretly took the body to Venice). From this time until 948 the Venetian chronicles do not mention conflicts with the Croats, which would mean that the Venetians offered peace and paid tribute to the Croats.