King Louis XIV ruled France for 72 years from 1643 to 1715, the longest reign in European history. He centralized power around himself by weakening the nobility and strengthening the royal administration. Louis grew the French economy through policies like mercantilism but also accrued major debts through wars and lavish spending. By the end of his reign, Louis had expanded French lands, strengthened its military and economy, and established France as the dominant power in Europe.