Sanna Mirella Marin was born on 16 November 1985 in Helsinki. She also lived in Espoo and Pirkkala before moving to Tampere. Her parents separated when she was very young; the family faced financial problems and Marin's father, Lauri Marin,struggled with alcoholism. After her biological parents separated, Marin was brought up by her mother and her mother's female partner.

Marin graduated from the Pirkkala High School in 2004 at the age of 19.She worked in a bakery and as a cashier while studying, graduating with a bachelor's and master's degree in Administrative Science from the University of Tampere.

Early political career
Marin's political career was described by the BBC as "beginning at the age of 20", in the years following her high school graduation and beginning her affiliation with the Social Democratic Youth.Marin joined the Social Democratic Youth in 2006 and was its first vice president from 2010 to 2012. In 2008 she unsuccessfully ran for election to the City Council of Tampere, but stood again and was elected in the 2012 elections.She became chairman of the City Council within months, serving from 2013 to 2017. In 2017, she was re-elected to the City Council.She first gained prominence after video clips of her chairing contentious meetings were shared on YouTube.

Marin was elected second deputy chairman of the Social Democratic Party(SDP) in 2014. In 2015, she was elected to the Finnish Parliament as an MP from the electoral district of Pirkanmaa. Four years later, she was re-elected. On 6 June 2019, she became theMinister of Transport and Communications.

In December 2019, Marin was nominated by the Social Democratic Party to succeed Antti Rinne as the Prime Minister of Finland, but Rinne formally remained party leader until June 2020. In a narrow vote, Marin prevailed over Antti Lindtman. A majority of the ministers in her five-party cabinet are women, numbering 12 out of 19 at the time of the cabinet's formation. She is the third female head of government in Finland, after Anneli Jäätteenmäki and Mari Kiviniemi.

In January 2018, Marin and her partner, Markus Räikkönen had a daughter.In August 2020, Marin and Räikkönen, who works in communications, married at the prime minister's official residence, Kesäranta.Their permanent residence is in the Kaleva district of Tampere,but during the COVID-19 pandemic, they have resided at Kesäranta.She has said that, if she had the choice, she would move to the countryside.Marin describes herself as coming from a "rainbow family",as she was raised by two female parents.She was the first person in her family to attend university. Marin is a vegetarian.

On 23 August 2020, Marin was elected chair of the SDP, succeeding Antti Rinne.