Halldóra Sigvaldadóttir (died after 1544) was the last abbess of the Kirkjubæjar Abbey on Iceland. Halldóra Sigvaldadóttir was the daughter of Sigvalda Gunnarssonar langalífs, who had a secular position within the church. She is described as a tall woman, in which she resembled her father. The year of her birth is unknown. She is likely to have become abbess just before the year 1500; the last abbess known before her was Oddný, who was mentioned in office in 1488. Her niece Oddný later joined her as a nun in the convent.