Muguruza, winner of the 2016 French Open and 2017 Wimbledon titles, capped a 2021 campaign that saw her return to the highest level with titles in Dubai and Chicago after three years outside of the top 10.
Muguruza, a former world number one, is projected to end the year at number three in the world.
Kontaveit, whose late-season surge included titles at Moscow and Cluj-Napoca, is projected to reach a career-high ranking of seventh in the world.
She notched her second win of the tournament against Kontaveit, having ended the Estonian’s 12-match WTA win streak with a must-have round-robin victory on Sunday.
“I’d like to congratulate Garbine,” Kontaveit said as she accepted her runner-up award.
“You’ve beaten me twice this week, that’s just too good.”
For Muguruza it was another standout performance in Mexico, where she won back-to-back titles in Monterrey in 2018 and 2019.
The WTA Finals were moved to Guadalajara from Shenzhen, China, because of the coronavirus pandemic. — AFP