Halimah was born in 23 August 1954, in the Colony of Singapore.
Halimah was educated at Singapore Chinese Girls' School and Tanjong Katong Girls' School before she went on to the University of Singapore, where she obtained a Bachelor of Laws in 1978.
Halimah married to Mohammed Abdullah Alhabshee, a Malay of Arab descent.
Halimah worked as a legal officer at the National Trades Union Congress, and became the director of its legal services department in 1992.
She was appointed as a director of the Singapore Institute of Labour Studies (now known as the Ong Teng Cheong Institute of Labour Studies) in 1999.
In 2001, she completed a Master of Laws at the National University of Singapore (NUS), and was conferred an honorary Doctor of Laws by NUS on 7 July 2016.
Halimah entered politics in 2001 when she was elected as an Member of Parliament (MP) for the Jurong Group Representation Constituency (GRC).
In recognition of her contributions, she was conferred the "Her World Woman of the Year Award" in 2003
Following the 2011 general election, Halimah was appointed Minister of State at the Ministry of Community Development, Youth and Sports.
Following a Cabinet reshuffle in November 2012,she became a Minister of State at the Ministry of Social and Family Development.
On 8 January 2013, Prime Minister Lee Hsien Loong nominated Halimah to succeed Michael Palmer as Speaker of Parliament following Palmer's resignation after he was revealed to have had an extramarital affair.
She was elected Speaker on 14 January 2013, the first woman to hold the post in Singaporean history.
She was inducted into the Singapore Council of Women's Organisations's Singapore Women's Hall of Fame in 2014.
In January 2015, Halimah was co-opted into the PAP's Central Executive Committee, the party's highest decision-making body.
At the 2015 general election, Halimah was the sole minority candidate for the People's Action Party group contesting the then-newly formed Marsiling-Yew Tee GRC.
On 6 August 2017, Halimah announced that she would be stepping down as Speaker of Parliament and MP of Marsiling-Yew Tee the next day to run for the presidency in the 2017 presidential election.
In an interview published on 11 August 2017, Halimah gave her views on the reserved presidential election. She said that it "shows we don't only talk about multiracialism, but we talk about it in the context of meritocracy or opportunities for everyone, and we actually practise it".
On 25 August 2017, Halimah launched her official campaign website, including her campaign slogan "Do Good Do Together", which was criticised by many for being ungrammatical. She defended her slogan, explaining that it is meant to be catchy.
On 13 September 2017, she was returned President-elect in a walkover, as no other presidential candidate was issued the Certificate of Eligibility. She was sworn in the following day, becoming the first female president in the country's history.
In 14 September 2017, she became Chancellor of the National University of Singapore
Halimah's decision to stay in her HDB flat at Yishun raised security concerns and was met with disapproval by netizens who highlighted the inconvenience caused by the Presidential motorcade as well as the additional cost in maintaining such security arrangement. On 2 October 2017, Halimah had accepted the government's decision to move her out of her Yishun flat to a more secure location. The government keeps track on the residence and security arrangements for her as well.