Nadal improved to 38-1 at Roland Garros, with the only loss to Soderling in the fourth round a year ago.
Seeded No. 2, Nadal won seven consecutive games midway through the match and held every serve, saving all eight break points he faced. He became the second man to win the French Open at least five times, and next year he'll have a chance to match Bjorn Borg's record of six titles.
Soderling finished as the runner-up for the second year in a row.