Vlad III of Wallachia, known as Vlad the Impaler was, in reality, a 15th-century prince of Wallachia (in modern-day Romania) who lived from 1431 to 1476 and reigned from 1448 to 1476 (except the years when he was imprisonned). He was also known as Vlad Drăculea. Drăculea is a diminutive form of his father's nickname Dracul (from his membership of the Order of the Dragon, Dracul meaning "Dragon" and "Devil" in Romanian). This word became Anglicised to Dracula and Bram Stoker used this form as the name of the titular vampire in his 1897 book Dracula.
In Romanian, Vlad the Impaler is translated to Vlad Ţepeş, and some Castlevania games give Dracula's full name as Dracula Vlad Ţepeş (or variations thereupon), implying a link between the two. However, in Castlevania: Lament of Innocence, Dracula was identified with Mathias Cronqvist, a fictional 11th-century Crusader who lived 400 years before Vlad the Impaler. Because of this, the position (and existence) of Vlad in Castlevania continuity is unclear. Presumably, in the 15th century, Mathias changed his name to Vlad Ţepeş and committed the atrocities which, in time, would become associated with a historical character. It is also possible that Mathias liked Vlad's surname of Dracula, and adopted it after Lisa was killed. Dracula originally meant "son of the dragon" but, in time, it would come to mean "son of the devil", a name Mathias would naturally be attracted to.
More interesting information is, the existence of Matthias Corvinus of Hungary; a man who took Vlad as vassal during a few years because he was married to his cousin, Ilona Szilagyi. His name ressembles a lot to Mathias Cronqvist, the man who would became Dracula in Castlevania: Lament of Innocence. It is said that Matthias Corvinus, after a request from Christian rulers, was obliged to imprison Vlad during 12 years. The fictional character Mathias Cronqvist's name would be created from Corvinus'. Another speculation would be the imprisonment: Joachim Armster is imprisoned in the Dark Palace of Waterfalls by Walter Bernhard.