Reyne Rebellion

The Reyne Rebellion was an uprising which occurred in the Westerlands, when House Reyne of Castamere tried to rise against House Lannister of Casterly Rock. House Reyne perceived that their Lannister overlords were weak, due to the incompetent leadership of the House's current head, Tytos Lannister. Tytos' son, the young Tywin Lannister, led his House's armies to crush the revolt. Unlike his father, Tywin was ruthless and cunning, and soon he defeated the Reynes and torched Castamere. Tywin executed any surviving Reynes, to make an example of them for any Lannister vassals who would dare challenge their dominance again.

The extinction of House Reyne marked the first major step in the return to glory of House Lannister, in which Tywin almost singlehandedly rebuilt the fortunes and strength of his House.

Tywin's victory was immortalized by the minstrels in the popular song, "The Rains of Castamere".

In the Books
There were actually two major Houses of the Westerlands that joined together to rise in rebellion against the Lannisters: House Reyne of Castamere and House Tarbeck of Tarbeck Hall. The Reynes and Tarbecks were the two most powerful vassals of the Lannisters at the time, but both were rendered extinct when Tywin crushed their revolt.