anna Marin will become the world's youngest sitting prime minister. Photo: Reuters

The transport minister was picked by her Social Democratic party after its leader, Antti Rinne, quit as PM. She will be sworn in this week.

She will lead a centre-left coalition with four other parties, all headed by women, three of whom are under 35.

Mr Rinne stepped down after losing the confidence of a coalition member over his handling of a postal strike.

When she takes office, Ms Marin will be the world's youngest sitting prime minister. New Zealand PM Jacinda Ardern is 39, while Ukrainian premier Oleksiy Honcharuk is 35.

What is Ms Marin's background?

Media reports say Sanna Marin was raised in a "rainbow family", living in a rented apartment with her mother and her mother's female partner. She told the Menaiset website (in Finnish) in 2015 that as a child she felt "invisible" because she was unable to talk openly about her family.

But she said her mother had always been supportive and made her believe she could do anything she wanted.

She was the first person in her family to go to university.

Ms Marin rose quickly through the ranks of the Social Democrats, heading the city administration in Tampere at the age of 27 and becoming an MP in 2015.

She has been transport and communications minister since June and has a 22-month-old daughter.