Takako Doi, a former House of Representatives speaker and onetime head of the Social Democratic Party, died of pneumonia on Sept. 20, the SDP said Sunday. She was 85.

Doi, who served as a Lower House member for 12 terms from 1969 to 2005, led the predecessor of the SDP from 1986 to 1991 as the first female leader of a major Japanese political party. She again took the helm of the party in 1996, when it renamed itself, and continued in the post until 2003.

A constitutional scholar, Doi was regarded as one of the highest-profile female pioneers in the male-dominated field of Japanese politics.