Vukan I (Serbian: Вукан, Greek: Βολκάνος; c. 1050 – 1112) was the Grand Prince of Serbia from 1083 until he died in 1112. During their first years he ruled together with his brother Marko. With the death of his uncle, King Constantine Bodin of Duklja in 1101, he became the most powerful ruler among Serbian princes. He defeated the Byzantines several times, conquering parts of northern Macedonia. He is the eponymous founder of the Vukanović dynasty.

Vukan was the first-born of Petrislav, the son of King Mihailo I and his second Greek wife. He and his brother Marko swore an oath of loyalty to Constantine Bodin and took power as his vassals in Serbia in 1083 or 1084. Marko later disappears from sources. Neither Bosnia, Zachlumia, nor Raška (i.e. Serbia) were ever permanently integrated into the Kingdom of Duklja. Each region had its nobility and institutions and acquired a Vojislavljević to head as Župan.

In 1089, Bodin managed to raise the bishopric of Bar to an Archbishopric, by supporting the pope against an antipope. The suffragan bishops were to be: Kotor, Ulcinj, Svac, Skadar, Drivast, Pula, Ras, Bosnia, and Trebinje. In obtaining its promotion, it acquired a much larger diocese, including territory that earlier had not been under the pope – territories of the metropolitan of Durazzo and Archbishop of Ochrid, two sees that recognized the jurisdiction of the Ecumenical Patriarchate of Constantinople. The Bar Archbishopric's new territory was merely theoretical – the pope's edict could only affect the churches that recognized Rome. Making Serbia a suffragan to Bar had little meaning, as most of its churches were under Constantinople, and there is no evidence of Vukan changing adherence to Rome. Durazzo and Ochrid may have suffered minimal territorial losses along the coast, Duklja was briefly a subject to Rome, however inland Duklja was not affected, and along with much of Duklja's coast (like most of Kotor) was to retain its loyalty to Orthodoxy.

A Byzantine campaign was launched against Duklja between 1089 and 1091, possibly managing to take Bodin captive for a second time. Civil war broke out in the realm among Bodin's relatives, greatly weakening Duklja, and giving the chance for inner Serbia to assert itself and break away. Vukan asserts independence, as well as Bosnia and Zahumlje. Up to this point, Duklja had been the center of the Serbian realm, as well as the main resistance to Byzantium in the Balkans. Inner Serbia became the most powerful of Serbian states, remaining so throughout the Middle Ages. Inner Serbia gradually replaced Duklja as the main opponent of Byzantine rule in the 12th century. Bodin's heirs were forced to recognize Byzantine overlordship, and had now only the small territory of Duklja and Travunia.

In 1091 or 1092, Vukan became independent, taking the title of Grand Prince (Veliki Župan). Subordinate to him were local dukes (Župan, holding a territory equivalent of a county), who seem to have been more or less autonomous in the internal affairs of their counties, but who were obliged to be loyal to Vukan, and supporting him in battle. It seems that the dukes were hereditary holders of their counties, holding their land before Duklja annexed inner Serbia.

In about 1090, Vukan began raiding Byzantine territory, first in the vicinity of Kosovo. Initially the Byzantines were unable to take steps against Vukan, as they faced a serious threat in the invading Pechenegs. On 29 April 1091, the Byzantines destroyed the Pecheneg force. With the defeat of the Pechenegs, Alexios I Komnenos could now turn to the Serbs.

Alexios I first sent an army with the strategos of Durazzo, which was defeated by Vukan in 1092. The Emperor now mobilized a much larger army, led by himself, marching onto inner Serbia. Vukan sends envoys, seeking peace which Alexios I quickly accepted, as a new problem had arisen at home in the Cumans who plundered the lands as far as Adrianople. Immediately after the Emperor's departure, Vukan breaks the treaty, and began to expand along the Vardar, obtaining much booty and taking the cities of Vranje, Skopje and Tetovo. In 1094 or 1095, Alexios I marched out to meet the Serbs. Vukan and his dukes arrive at the Emperor's tent and offer peace, with his own son Uroš I as hostage (throughout the 12th century it was usual for relatives of the Grand Prince to stay at the imperial court as hostages of peace).

At this time, Serbian principality was independent – Vukan acted entirely on his own, no longer a vassal of Duklja. Duklja, because of its civil war, did not involve itself in the Serbian-Byzantine wars.