Helena of Serbia (Serbian: Јелена/Jelena, Hungarian: Ilona; b. after 1109 – after 1146) was Queen of Hungary as the wife of King Béla II, who reigned from 1131 to 1141. A daughter of Prince Uroš I of Serbia (r. ca. 1112–1145), she was arranged to marry Béla II in 1129 by his cousin, King Stephen II (r. 1116–1131). Béla II had been blinded on the order of Stephen's father, King Coloman. After her husband's death, she governed Hungary as regent from 1141 to September 1146 together with her brother, Beloš, when her eldest son, Géza II, came of age. Her younger sons, Ladislaus II and Stephen IV, also ruled as kings of Hungary.

Helena was the daughter of Serbian Grand Prince Uroš I (r. ca. 1112–1145) of the Vukanović dynasty, and Byzantine princess Anna Diogene. Her father had participated in the Byzantine-Hungarian War (1127–29), on the side of King Stephen II of Hungary. The Hungarian Army had destroyed Byzantine Belgrade and penetrated to Naissos (Niš), Serdica (Sofia) and Philippopolis (Plovdiv).

Around 1129, King Stephen II arranged her marriage with his cousin Béla, who had been blinded on the order of the king's father, King Coloman of Hungary (r. 1095–1116). Uroš I had prior to this suffered to both Hungary and Byzantium, so he happily befriended the Hungarian king. King Stephen II granted estates near Tolna to the newly wed couple.

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