Little is known about Gunnlaugr's family or life, but a miracle in Jóns saga helga hin elsta describes how Gunnlaugr the Monk's "disciple and relative" Leifr recovers from a dangerous illness after drinking holy water touched by the relics of Bishop Jón Ögmundarson of Hólar.
This work is now lost but it is believed to have been an expansion of the Latin Óláfs saga Tryggvasonar written by his monastic brother, Oddr Snorrason.
Gunnlaugr also composed the original Latin version of Þorvalds þáttr víðförla but it is only preserved in an Old Norse translation.
One study hypothesizes that the extant Old Norse translation of Vita sancti Ambrosii, Ambrósíus saga, may be Gunnlaugr's work,[5] although Gunnlaugr's nova historia sancti Ambrosii is generally identified as a Latin office of St Ambrose, Ambrósíustíðir.
[6] Gunnlaugr is likewise credited with the poem Merlínússpá, a Norse translation of Prophetiae Merlini by Geoffrey of Monmouth.