Last name Guðný (Guðný 
) , in all the world, is an extremely rare cognomen. Much more frequently, Guðný is the forename as well as the last name.
Eygló, Ólafsdóttir, Björnsdóttir, Bjarnadóttir, Ríkarðsdóttir, Gísladóttir, Jóhannsdóttir, Einarsdóttir, Friðriksdóttir, Ingólfsdóttir, Þórðardóttir, Þorsteinsdóttir, Kjartansdóttir, Ragnarsdóttir, Gunnarsdóttir, Guðmundsdóttir, Halldórsdóttir, Hallgrímsdóttir, Sigurðardóttir, Benediktsdóttir, Kristinsdóttir, Kristjánsdóttir, Árnadóttir, Tómasdóttir, Jónasdóttir, Guðjónsdóttir, Waage, Óladóttir, Atladóttir, Björg, Ingadóttir, Óðinsdóttir, Þóra, Pálsdóttir, Leifsdóttir, Jensdóttir, Vilhjálmsdóttir, Jónsdóttir, Hauksdóttir, Helgadóttir, Ævarsdóttir, Magnúsdóttir, Snorradóttir, Arnardóttir, Arnþórsdóttir, Bragadóttir, Karlsdóttir, Guðnadóttir, Harðardóttir, and Þórarinsdóttir