Speaking at a National Day dinner at the Marsiling Mega Sports Park, the Marsiling-Yew Tee GRC Member of Parliament (MP) said: "I recognise that the position of the elected President has the tremendous capacity to do good for all Singaporeans and for Singapore.
"Hence, I wish to inform you that I will be contesting in the coming Presidential Election."
Mdm Halimah also said she will resign on Monday from her roles as Speaker of Parliament and MP.
She said she will ask Prime Minister Lee Hsien Loong in her resignation letter to consider sending an adviser to support the work of the other Marsiling-Yew Tee GRC MPs Lawrence Wong, Alex Yam and Ong Teng Koon.
Mdm Halimah also said that she has asked the Prime Minister to look into making "quick replacements" for the appointments she is holding.
Speaking to media on the sidelines of the dinner, Mdm Halimah said it took her some time to make a decision as the role of the President was a "very heavy, onerous responsibility" that "had to be carefully considered".
She described leaving Marsiling-Yew Tee GRC as a "bittersweet" experience, and said residents have been supportive.
"I am deeply humbled and honoured that Singaporeans have asked me to consider running for the elected presidency," said Mdm Halimah in a media statement.
In the statement, she reiterated that she had had to consult "extensively" with her family, colleagues and close friends in order to make what she called a "tough decision".
National Development Minister Lawrence Wong said in a Facebook post that Mdm Halimah had discussed this "major decision" with him and the other Marsiling-Yew Tee MPs.
"In the last two years in Marsiling, Mdm Halimah has made a significant impact on the ground and made a difference in the lives of many residents," he said.
"My team and I will build on her good work and work even harder to serve our residents," he added.
Mdm Halimah also shared in a Facebook note late Sunday evening that she thought a president "should unify the nation and channel (its) shared values into doing good for the country, and wholeheartedly serve Singapore and Singaporeans".
"This is the kind of president I would like to have. This is the kind of president I would like to be," she said.
Since then, her heritage has come under some discussion. Under recent changes to the elected presidency, this year’s vote is reserved for the Malay community. Mdm Halimah’s late father was Indian-Muslim.
However, at a post-Hari Raya gathering of women leaders last month, she said she has been “certified four times by the Community Committee as a member of the Malay community”.
The committee is responsible for ascertaining if candidates belong to a particular racial community.
Mr Farid has also said he is confident of qualifying as a Malay candidate even though his identity card identifies him as Pakistani.
A third potential candidate is Mr Mohamed Salleh Marican, CEO of Second Chance Properties.
This year's Presidential Election will be held in September. Applications opened on Jun 1 and will close five days after the writ of election is issued sometime this month.