Girion is the ancestor and lord of Dale whose surviving descendant is Bard the Bowman.
In Tolkien’s account, Girion was the last Lord of Dale before Smaug attacked the city and the nearby dwarf kingdom of Erebor. During the destruction, Girion used black arrows against the dragon but could not defeat him. Girion’s wife and child escaped, preserving the line that eventually produced Bard.
Bard lives in Lake-town during The Hobbit and is described as a descendant of Girion. He kills Smaug with the Black Arrow after learning of the dragon’s vulnerable spot. Following the Battle of Five Armies, Bard helps restore Dale and becomes its king.
The wording can cause confusion because Tolkien’s texts identify Bard as a descendant rather than presenting Girion as Bard’s immediate father. Bard’s son is Bain, who succeeds him as king. Girion therefore belongs to the older history of Dale, before Smaug’s long occupation of Erebor.