Rodrik Stark

Rodrik Stark is an unseen character in Game of Thrones. He is dead by the time in which the show takes place. He was a King in the North who, according to legend, won Bear Island in a wrestling match and then granted House Mormont lordship over it.

In the books
In the A Song of Ice and Fire books, King Rodrik Stark's story is the same. Presumably he took Bear Island from the ironborn, who under the rule of Qhored Hoare ruled much of the western coast of Westeros, from Bear Island to the Arbor.