Paganija or Pagania or Narenta or Neretva
"It should be known that the en:Serbs originate from the pagan Serbs, also called en:White Serbs, who live on the other side of Hungary ("Turcia") [...] Due to the fact that present-day en:Serbia and en:Pagania (Paganoi)... the emperor settled the same Serbs in these lands, and they were under his tutelage; the emperor Christianized them with Roman priests".
Constantine VII, De Administrando Imperio, Chapter: 32 []
Pagania bordered the lands of Zahumlje to the north and northeast and Croatia to the west. It's coast encompassed the northern half of what is today the Split-Dalmatia county along with the cities of Sinj, Imotski, Vrgorac, Split including Katela and Soli, as well as towns off the coast such as Trogir, Omi, and Makarska the islands of Brac, Hvar, Stari Grad, Vis and Komia.
Constantine VII Porphyrogenitos descibes the Paganians in De Administrando Imperio as a Serb tribe which settled in present Hercegovina around the Neretva River at the start of the 7th century. Pagania entered into confederations with the Serb princes of Raska early on. The Serb prince Caslav Klonimirovic of the House of Vlastimirovic fully incorporated this area into his domain between 927 AD and and 940. The Serb prince Caslav Klonimirovic of the House of Vlastimirovic fully incorporated this area into his domain between 927 AD and and 940. After the death of Caslav in 960, Travunia was contested between Byzantium and Bulgaria. But by 968, it was violently conquered by the Croatian King Kresimir but it returned to the Serb princes of the House of Vojislavljevic of Zeta by the middle of the 11th century and later to Serb princes of the House of Nemanjic of Raska.
Croatian academics have pointed out that Pagania could have been Croats, but this is not generally accepted since these claims rely on Chronicle of the Priest of Duklja, which has been discredited as unreliable and full of errors. It is now accepted in most academic circles outside of Croatia that Travunia / Travunja , Zachumlie / Zahumlje, Bosnia / Bosna and Zeta / Duklja were settled with Serb tribes, as it states in De Administrando Imperio.