The social media entrepreneur tweeted to his followers he wanted to help "disarm this pandemic".
Jack - who also founded payments app Square - revealed the donation is about 28% of his wealth.
He said last night (Tuesday April 7) that equity from Square would be put into a charitable fund called Start Small to "fund global Covid-19 relief".
Sharing a document tracking all operations to ensure transparency, he noted that the fund's focus would eventually shift to girl’s health and education, and Universal Basic Income.
Life is too short, so let's do everything we can today to help people now.
Jack wrote: "Why now? The needs are increasingly urgent, and I want to see the impact in my lifetime.
"I hope this inspires others to do something similar.
"Life is too short, so let's do everything we can today to help people now."
And addressing the fund’s wider goals, the 43-year-old noted he hoped for a long-term impact.
"Why UBI and girl’s health and education?" Jack tweeted.
"I believe they represent the best long-term solutions to the existential problems facing the world."
He said he was using shares of Square and not Twitter because he owned "a lot more" of them.
It is believed the shares will be sold over time, which could impact on their value and size of the donation.
The Twitter boss is not the only tech billionaire to donate part of their wealth towards coronavirus-related efforts.
'The biggest single donation to tackling coronavirus'
However, his pledge is by far the biggest single donation to tackling the pandemic.
Amazon owner Jeff Bezos has donated $100m to food banks in the US.
He said in an Instagram post: “Even in ordinary times, food insecurity in American households is an important problem.
"And unfortunately Covid-19 is amplifying that stress significantly."
Facebook founder Mark Zuckerberg has also committed $30million.
It is believed the majority of that amount will be focused on trying to create a treatment for coronavirus.
The Bill & Melinda Gates Foundation has donated $100million to similarly develop a vaccine and fund testing.
Michael Dell - the founder of Dell computers - has offered $100million.
And Apple chief executive Tim Cook has also announced the company will donate medical supplies to support hard-hit Italy.
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