Ostapenko, unseeded and ranked 24th in the world heading into the final, won 6-4, 6-1 to win her first title on clay since her 2017 French Open triumph.
The Latvian cruised to victory, converting her first match point to lift her first WTA singles trophy since February last year.
“It’s great to share the court with you – you’re a champion,” Ostapenko said to Sabalenka in her on-court interview.
Three-time Grand Slam champion Sabalenka has now lost four finals in Stuttgart in the past five seasons.
“I’m sure you hate me now because you wanted this car so badly, but I’m sure you’ll get it another time,” Ostapenko added of the car that tournament winners receive as a bonus prize.
The 26-year-old Sabalenka, who won the 2024 US and Australian Opens, is still waiting for her first tournament victory on clay since the 2023 Madrid Open.
“You were a better player than me, that’s all there is to it,” Sabalenka said.
Ostapenko broke her opponent in the very first game of the match to set the tone.
She did the same in the opening game of the second set, which appeared to break Sabalenka’s resistance, with the Belarusian growing increasingly frustrated.
At one point, Sabalenka fell to the clay, but signalled to her opponent and the umpire that she was not injured.
The tournament win completes an impressive week for Ostapenko in Germany.
She defeated five-time Grand Slam winner Iga Swiatek, ranked second, in the quarters before a straight-sets victory over Ekaterina Alexandrova in the semi-finals.
Ostapenko will climb six places in the WTA rankings to 18th after her first win over Sabalenka at the fourth attempt. (AFP)
