I'm not too familiar with the western societies but in Asia I can name one in detail. One was Empress Seondeok(선덕) of Silla during 632-647AD. She was directly selected by the previous emperor Jinpyeong (진평) because he had no sons. She helped stabilize the Silla empire during a violent rebellion and helped cultivate culture and strengthened Buddhism during her rule. She built the 첨성대, which is the first East-Asian observatory, decreased poverty in the region, as well as avoiding conflict with Baekjae and Goguryeo through excellent diplomacy.

She was the second female sovereign in Asia. I don't know about the first one.

I don't have sources but I learned this during my high school history class in Korea. If this isn't suitable, please remove this post.

Anyone else? Or we've been living in a sexist world far too long?