Rhiwaedog is the name of an ancient estate in North Wales, located in the Penllyn forest near Bala, Gwynedd. It gives its name today to two hills, Rhiwaedog-is-Afon and Rhiwaedog-uwch-Afon, meaning "Rhiwaedog below the river" and "Rhiwaedog above the river" respectively. There is also the ancient manor house Plas Rhiwaedog, from which Rhirid Flaidd (also known as Rhirid ap Gwrgenau) (fl. 1160) ruled his demesne.