SAN FRANCISCO — Jack Dorsey, the chief executive of Twitter and Square, said on Tuesday that he planned to donate $1 billion, or just under a third of his total wealth, to relief programs related to the coronavirus, in one of the more significant efforts by a tech billionaire to fight the pandemic.

Mr. Dorsey said he would put 28 percent of his wealth, in the form of shares in his mobile payments company Square, into a limited liability company that he had created, called Start Small. Start Small would make grants to beneficiaries, he said, with the expenditures to be recorded in a publicly accessible Google document.

“Why now? The needs are increasingly urgent, and I want to see the impact in my lifetime,” Mr. Dorsey said in a series of tweets announcing his plans. “I hope this inspires others to do something similar.”