Sharapova has struggled with her serve this week and had 12 double-faults in the final on Court Philippe Chatrier. But she was able to hold off Halep, and hold her serve in the final game, with steady groundstrokes that kept the Romanian on the run.
Sharapova also won the title at Roland Garros in 2012, completing a career Grand Slam. She lost in last year's final to Serena Williams.
Halep, who was ranked only 57th heading into last year's French Open, was playing in her first major final.
"This is the toughest Grand Slam final I've ever played. All respect to Simona, I thought she played unbelievable," Sharapova said.
-- The Associated Press