The top-seeded Halep, who went unbeaten through the group stage, played with a muscle strain in her left leg but still managed to win the last five games of the third set to close out the victory. Halep won 20 of the last 26 points, finishing it off with a forehand winner down the line.
Halep enjoyed a majority of the crowd support, with a large contingent of supporters from neighboring Romania.
"I want to thank all my supporters here, who came to support me and helped me win the title," Halep said.
Halep repeatedly moved Stosur into the corners and finished off several points with perfect shots down the line.
"It was a tough match, Simona was too good today," Stosur said. "I want to congratulate her. For me, it's time to get some rest."
By winning six trophies this year, Halep is second only to Serena Williams, who won 11.
Halep is expected to rise to No. 11 in Monday's WTA rankings.