The 64-year-old conservative is known as Japan's 'Iron Lady' and she's an admirer of former British Prime Minister Margaret Thatcher.
This is her third attempt at becoming the Japanese leader, and she's the fourth PM in five years from her scandal-hit party, LDP.
She is also a protege of the late former PM Shinzo Abe.
Now that she's elected, her many challenges will include contending with a sluggish economy, navigating a rocky US-Japan relationship and uniting the ruling party which has been rocked by scandals and internal conflicts.
Source - BBC