Hróa þáttr heimska or the Tale of Roi the Fool is a short story (þáttr) from Iceland about a Dane called Hrói the Fool who is helped in a legal dispute by the wise old Swede Þorgnýr the Lawspeaker, and which takes place in the late 10th century. It is preserved in two versions of which one (HróFlat) is found in Flatey Book (GKS 1005 fol 344-348, ca 1387-1395) and the second one (Hró AM 557 4°) in the Skálholtsbók (AM 557 4° 41r-42v, ca 1420-1450) in Copenhagen.
In the version of Óláfs saga helga which is found in the Flatey Book, it is inserted together with Styrbjarnar þáttr Svíakappa in the description of Olaf Haraldsson's wooing of the Swedish princess Ingegerd Olofsdotter. Their purpose appears to be to present the Swedish court, its traditions and Þorgnýr the Lawspeaker.