Domanek (Serbian Cyrillic: Доманек; Latin: Domanec; fl. 1054–55) was a local Slavic chieftain from the region surrounding Trebinje. After a revolt and the murder of earlier ruler of Travunia (ca. 1054–1055), the rebel chieftains made Domanek their leader and a ruler of Travunia.^[2]

According to the Chronicle of the Priest of Dioclea, when Stefan Vojislav, the Grand Prince of Duklja, died, the lands were divided between his widow and five sons.^[2][3] Gojislav received the Trebinje region.^[3] The local nobles eventually rose up and killed him.^[3] The nobles then set up one of their own, Domanek, as prince, in ca. 1054.^[2][3][1]

Mihailo I, the holder of Duklja (the crownland), and two of his brothers, led an attack into Travunia, capturing the murderers and giving "them a horrible death".^[2][3] Domanek fled the lands, and Saganek, another brother of Mihailo, succeeded as the rightful Prince of Travunia.^[3] Domanek returned shortly after Mihailo's departure, and expelled Saganek.^[3] Mihailo offered the office to Radoslav, who declined, afraid of losing Luška župa (future Zeta).^[2][3] Radoslav perhaps distrusted his brother, thinking he would seize Zeta, but Mihailo seems to have offered him a deal.^[3]

The Byzantine Empire, wanting to take advantage of the death of Stefan Vojislav, prepared an offensive against unstable Duklja.^[3] At this time, the four remaining brothers made peace and established an alliance.^[3] The treaty concluded is the oldest in Serbian history.^[3] After the agreement, Radoslav attacked Trebinje, killing Domanek.^[3] Radoslav went on to conquer Zahumlje.^[2]

• Fine, John Van Antwerp (1991). The Early Medieval Balkans: A Critical Survey from the Sixth to the Late Twelfth Century. Michigan: The University of Michigan Press. ISBN 0-472-08149-7.
• Paul Stephenson, Byzantium's Balkan frontier: a political study of the Northern Balkans, 900-1204