"Amina Sarauniya Zazzau" -- Queen Amina of Zazzau or Zaria, now a province of Nigeria, was a leader of the Hausa people. She was born about 1533, the oldest daughter of Bakwa Turunku (one site refers to this ruler as a woman but another says the gender is not certain); Amina came to power about 1588 after a ten-year-period of rule by her younger brother Karama. During her brother's reign, Amina, who had spent much time on her military skills, emerged as the kingdom's leading warrior of the cavalry. This was important as Zazzau was a trading city-state and needed power to provide safe passage for its traders.

When she came to power, she put all her lands' force behind her expeditions; the first one started a bare three months after her accession to the throne. She expanded Zazzau to its largest size ever and made other rulers her vassals to ensure that caravans of merchandise could pass. Legend says she built a walled camp in every area that her forces conquered and popularized the earthen fortifications around towns that are still used on Hausa settlements and called "Amina's walls" in the area. She never married permanently, but is rumored to have taken a "temporary husband" in each new location and dropped him (or killed him) when she left. She reigned for more than 30 years and is still remembered as "a woman as capable as a man."

Sources:
http://www.abcorpaffairs.com/gallery/21gal.htm
http://www.distinguishedwomen.com/biographies/zazzua.html
http://www.ngex.com/nigeria/places/states/kaduna.htm
http://www.bbc.co.uk/worldservice/africa/features/storyofafrica/4chapter5.shtml