Warren Buffett, the second-richest person in the U.S., made his largest single charitable contribution ever when he donated $2.1 billion to the Bill and Melinda Gates Foundation.

The chairman and chief executive officer of Omaha, Nebraska-based Berkshire Hathaway Inc. gave 16.6 million Class B shares yesterday in an annual gift to the foundation, where he is a trustee, according to a regulatory filing today. The donation beat last year’s record gift of $2 billion, when he gave 17.5 million shares. The stock has gained 8.8 percent this year through the close of trading yesterday to $128.98.

Buffett, 83, has vowed through the Giving Pledge initiative to give away most of his net worth, which is more than $60 billion, according to the Bloomberg Billionaire’s Index, a daily ranking of the world’s wealthiest people. Along with Microsoft Corp. co-founder Gates, the world’s richest man, he has urged other ultra-wealthy people to give away their money.

“I will give 99 percent, but the other 1 percent is way more than enough,” Buffett said June 9 at the Edison Electric Institute annual convention in Las Vegas. “I have never given a dollar that caused me to give up something I wanted to buy.”

Family Charities

Most of Buffett’s donations go to the Gates Foundation, which focuses on hunger, poverty and education. He earmarked 10 million Class B Berkshire shares for the Seattle-based charity in 2006 and gives 5 percent of the remaining total each year. The shares were split 50-1 in 2010. Including the latest gift, he has given shares valued at more than $15 billion, based on their price at the time they were turned over.

The billionaire also made gifts yesterday of 1.2 million Class B shares yesterday to each of his children’s philanthropies. They are the Howard G. Buffett Foundation, which works on solving conflicts and providing food to people in developing countries; the Sherwood Foundation, which targets education and social-justice issues in Nebraska; and the NoVo Foundation, a New York charity seeking to establish equality for women.

He also donated 1.7 million Class B shares, worth about $214 million based on yesterday’s closing price, to the Susan Thompson Buffett Foundation. The education-focused charity is named for the billionaire’s first wife, who died in 2004.