Ffernfael ap Tewdwr (English: Ffernfael, son of Tewdwr; Old Welsh: Fernmail map Teudur; fl. c. 830) was a king of Buellt and Gwrtheyrnion in medieval Wales. Little is known of him besides a pedigree included in the 9th-century Historia Brittonum, which makes him a descendant of the ruler Vortigern.