No. 1: Mark Zuckerberg and Priscilla Chan

Amount donated in 2013: $992.2-million

Beneficiary: Silicon Valley Community Foundation

Background: Mr. Zuckerberg is co-founder and chief executive of Facebook. Ms. Chan is a pediatrician.

The couple gave 18 million shares of Facebook, valued at about $992.2-million, to the Silicon Valley Community Foundation, in Mountain View, Calif. They donated the same number of shares in Facebook to the fund in 2012.

In 2010, Mr. Zuckerberg, now  29, pledged $100-million to establish Startup: Education, a foundation to support programs to improve public schools in Newark, N.J. He is a board member of Startup: Education.

Mr. Zuckerberg did not say what programs the latest gift would support but said that their philanthropy would focus on children.

The Philanthropy 50: Browse the full list of America's most generous donors in 2013.

Learn more: See these donors' listing in our database of major gifts, America's Top Donors.