Jo Cox, the MP for Batley and Spen, died from her injuries sustained in the horrific attack on Thursday.
The Batley and Spen MP was shot and stabbed by a man in Market Street at 12.53pm.
She was taken to Leeds General Infirmary but tragically passed away from her injuries.
West Yorkshire Police has launched a murder investigation into the senseless attack.
A 52 year old man named locally as Thomas Mair was arrested.
At a press conference, temporary Chief Constable Dee Collins said: "I am very sad to report she has died. I would like to express our deepest sympathies to her family and friends at this time.
"This is a very significant investigation. A full investigation is underway to establish the motive of this attack."
Reports that someone had been shot in Birstall shortly surfaced on social media around 1pm.
Social media rumours around 10 minutes later first suggested the victim was Batley and Spen MP Jo Cox. It is understood she was left lying severely injured on the pavement near Birstall library.
An eyewitness told the Examiner the man was shouting what sounded like "Britain First, Britain First."
A man in his late 40s to early 50s was slightly injured in the same incident.
This picture of the man said to be the attacker being arrested was circulating on social media but reports are unconfirmed.
Armed police were outside Leeds General Infirmary so it was understood Ms Cox was taken there for specialist high dependency treatment.
Labour shut its constituency offices in an emergency measure.
Shortly before 3pm the Vote Leave campaign suspended its Battle Bus.
Ms Cox was a supporter of the Remain campaign and reports are circulating that the attack was carried out by a man who shouted “Britain first.”
Jo Cox murder - how events unfolded
How events unfolded during the day
The MP in profile
Everything we know about what happened
Britain First leader says killer 'probably wasn't a member' of far right group
Jo Cox has tragically died of her injuries
Jo Cox obituary
Jo Cox's husband Brendan's statement
Police statement in full
Hero police tacked suspect despite being unarmed and not wearing stab vests
Tears and sadness at the vigil in Jo's memory
Book of condolence opened in Batley
A local campaigner
More than £1,000,000 raised for Jo
Online condolence book
Terrorism link probed
Thomas Mair charged with murder
Mair's first court appearance
"He never spoke to anyone"
Tributes from Jo's devastated family
A hero tried to save her
"A good Samaritan"
Main parties won't contest Batley and Spen seat
MPs wore white roses in Jo's honour
Hero Bernard Kenny who tried to save Jo
Tributes to JoLight sculpture created for Jo Cox memorial service in Huddersfield tonight
People pay tribute to Jo on her birthday
Mair's first appearance in crown court
MPs pay tribute in parliament
More than £1,000,000 in four days in Jo's memory
Calls for Bernard to receive the highest honour
Jo worked hard to support refugees