In modern history, who was the first female leader of a national government?

Sirimavo Bandaranaike (17 April 1916 – 10 October 2000), was a Sri Lankan stateswoman and politician and the modern world's first female head of government. She entered politics shortly after her husband's (Prime Minister Solomon Bandaranaike) assassination. She served as Prime Minister of Ceylon and Sri Lanka three times, 1960–65, 1970–77 and 1994–2000.

Her husband, Solomon, became Prime Minister in 1956. He had his tenure cut short three years later when he was assassinated by a Buddhist monk on 26 September 1959. The assassination created a power vacuum, due to Solomon's likely successor Charles de Silva (leader of the House of Representatives and Finance Minister) being gravely ill and in London for treatment at the time. Wijeyananda Dahanayake, Minister of Education, was appointed interim Prime Minister. Turmoil in the government followed as Dahanayake sacked and appointed ministers.

During this time Sirimavo was brought forward as legitimate successor to her husband's party leadership and she entered politics. In 1960 Senator de Zoysa Jr stepped down from his seat in the Senate paving the way for Sirimavo to be appointed as a member of the Senate. She pledged to continue her husband's policies and soon afterwards led her party to win the July 1960 elections becoming the first female prime minister in the world.

The second female prime minister in the world was Indira Gandhi of India.