Hallbera Þorsteinsdóttir

Hallbera Þorsteinsdóttir (died 1330; Old Norse: ; Modern Icelandic: ) was the founder and abbess of the convent Reynistaðarklaustur of the Benedictine order on Iceland.

Hallbera belonged to a wealthy and powerful Icelandic family. She was the daughter of Abbot of Hestur and later Stórólfshvoll and of the Oddaverjar. Her sister, , was married to the chieftain Kolbeinn Bjarnason, but Hallbera's marital status prior to joining the abbey is not mentioned in contemporary sources. She could have lived as a financially independent widow before turning to a religious life, as was not uncommon for aristocratic women in Iceland at the time. In 1295, Hallbera donated vast lands to the foundation of a convent for nuns of the order of Saint Benedict. but scholars Ármann Jakobsson and Ásdís Egilsdóttir also identify her as the "Sister Katrín" who was Reynistaðarklaustur's first abbess, arguing that Katrín was Hallbera's religious name. Sister Katrín otherwise served as abbess for only one year before vanishing from all sources. If Hallbera and Sister Kristín are the same person, then she lived at Munkaþverá as a nun or anchorite prior to the founding of and was an educated and literate woman for whom the religious name Katrín (Catherine) would have been highly appropriate.

Hallbera had a close professional relationship to the Bishops of Holar, Auðunn rauði Þorbergsson and Lárentíus Kálfsson, who respected her opinion. The latter dedicated several poems to her.