TOKYO — Renho Murata became the first woman to lead the opposition Democratic Party in Japan after winning a leadership contest on Thursday.

Ms. Murata, who has served in the country’s upper house of Parliament for more than a decade, won in a landslide against two male competitors despite controversy over her part-Taiwanese heritage.

By winning the leadership contest, Ms. Murata, who is widely known by just her first name, became the third woman to take up a prominent political job in Japan in less than two months, heralding a budding shift in a country with an abysmal track record of putting women in power.

In her final speech before the vote, Ms. Murata, a former model and television news anchor, spoke emotionally about her children, 19-year-old twins, and how she was sometimes frustrated trying to balance work and motherhood.