The announcement comes one month after the couple who co-founded the foundation said they had filed for divorce.
In a statement, Buffett did not state why he was leaving the board at this time, only that he has been inactive in his role, quote: "For years I have been a trustee - an inactive trustee at that - of only one recipient of my funds, the Bill and Melinda Gates Foundation. I am now resigning from that post, just as I have done at all corporate boards other than Berkshire's."
Bill Gates and his wife Melinda, co-founders of the foundation, filed for divorce in May after 27 years of marriage but have pledged to continue their philanthropic work together. The 21-year-old foundation has become one of the most powerful and influential forces in global public health, spending more than $50 billion over the past two decades to bring a business approach to combating poverty and disease.
Buffett also said in the statement that he delivered another $4.1 billion worth of his Berkshire Hathaway stock to philanthropy, saying he was halfway toward reaching his goal of giving away about 99% of his net worth.
Last year, he reported donating more than $2 billion worth of his Berkshire stock to the Gates Foundation.
Buffett and Gates pioneered "The Giving Pledge" campaign that urges billionaires to donate at least half of their fortunes to charity.
