Béla I (Hungarian: I. Béla, Slovak: Belo I), was king of Hungary between 1061 and 1063. Baptized as Magnus, Béla was his pagan given name. Béla was a member of the Árpád dynasty, third son of Vazul and younger brother of András I who was crowned king after the Vatha pagan rising.

In 1048, András conferred to Béla one third of Hungary as appanage ("Tercia pars Regni"), making him Duke of the Nitrian Frontier Duchy, whose capital was Nitra and which involved the southern Slovakian Nitrian Principality and the northeastern historic Hungarian Bihar region (not identical to the later Bihar).

The two brothers shared power without incident until 1053, when András fathered a son. Thereafter, András became determined to secure the throne for his son and to displace his brother. András therefore had his son (Béla's nephew) Solomon crowned future king in 1057. According to legend, András placed before Béla a crown and a sword, representing royal and ducal power, respectively, and asked Béla to take his choice. Knowing that chosing the crown would mean his life, Béla instead selected the sword. In 1059, Béla fled to Poland where he was received by his brother-in-law Boleslaus II of Poland, brother of Béla's wife Richeza.

In 1060, Béla returned to Hungary and defeated András I to become the new king. After András' death, Béla was crowned king on December 6, 1060. During his brief reign he concerned himself with crushing pagan revolts in his kingdom. Béla died in an accident when his throne's canopy collapsed while sitting on it. After Béla's death in 1063, Henry III, Holy Roman Emperor installed Solomon as the new king and his male progenies had to flee to Poland again.

Béla's and Richeza's children included:
1. Géza, ruled as king 1074-1077
2. László (Ladislaus), ruled as king 1077-1095
3. Lampert, duke of Nitra 1077-1095
4. Zsófia or Sofia, (d. 18 June 1095); First marriage c. 1062 with Ulrich I von Weimar, Markgraf of Carniola, Count of Istria (d. 1070); second marriage c. 1071 with Magnus, Duke of Saxony
5. Euphemia (Ludmilla), (d. 2 April 1111; Married with Prince Otto I of Moravia (d. 9 July 1087)
6. Illona (Helen), married to the king of Croatia Dmitar Zvonimir (1075-1089)
7. Maria, (b. c. 1053/55); Married with Andronicus Dukas, co-emperor of the Byzantine Empire, son of Constantine X
8. Adelhaid, (b. c. 1050, d. after 1104); Married with Count Friedrich II von Bogen