Lárentíus Kálfsson (medieval Icelandic Laurentius Kálfsson), 10 August 1267–16 April 1331) was bishop of the northern Icelandic diocese of Hólar 1324–31.
Laurentius studied first with Þórarinn kaggi, his maternal uncle, in Vellir in Svarfaðardalur and later with Jörundr Þorsteinsson, the bishop of Hólar, and became renowned for his learning. He spent much of his career, however, in dispute with various powerful churchmen. He was consecrated as a priest in 1288 and was the schoolmaster at Hólar for the following three years, after which he was priest at Háls in Fnjóskadalur from 1292–1293. Following a dispute with the bishop of Hólar, he went to Norway in 1294 and there served Archbishop Jörundr, studying law with Jón the Fleming, and finding himself making enemies among the canons of the cathedral of Nidaros. Returning to Norway after an unsuccessful trip to Iceland in 1307-8, he was imprisoned by them, and sent back to Iceland in 1309 where he was able to join the monastery of Þykkvabær. The next bishop of Hólar was an old enemy of Laurentius's from among the canons of Nidaros, Auðunn rauði, with whom Laurentius made peace in the autumn of 1319, going on to teach Auðunn's grandson. On Auðunn's death in 1322, Laurentius succeeded him as bishop of Hólar, being consecrated in 1324.
Most of what we know about Laurentius comes from Laurentius saga, almost certainly written by Laurentius's one-time pupil and close friend Einarr Hafliðason (1307–93).
Laurentius had a son by a Norwegian woman: Árni Lárentíusson, later a monk at Þingeyraklaustur.