In her short career as one of the world’s leading philanthropists, MacKenzie Scott has made a mark through the enormous scale of her giving and also through its speed, donating nearly $6 billion of her fortune this year alone.

Ms. Scott, an author who was once married to Jeff Bezos, the founder and chief executive of Amazon, announced in a Medium post on Tuesday that she had given nearly $4.2 billion to 384 organizations in just the last four months. Many of the groups are focused on basic needs, including food banks and Meals on Wheels, in a trying year for millions of people.

“This pandemic has been a wrecking ball in the lives of Americans already struggling,” Ms. Scott wrote. “Economic losses and health outcomes alike have been worse for women, for people of color, and for people living in poverty. Meanwhile, it has substantially increased the wealth of billionaires.”

Mainstays like the N.A.A.C.P., Easterseals, Goodwill and the United Way made the list. So did more than 100 separate Y.M.C.A. and Y.W.C.A. organizations nationwide, which like many nonprofits have lost enormous amounts of revenue, even as demand for their services has increased.