The news ends speculation in recent weeks about the future of the newspaper following talks between the two partners.
Industry sources suggest that the New York Times has been concerned that the Herald has not been providing a return on investment, and the Times is thought to be keen to get the newspaper to pay its way.
It is unclear whether the Herald name will now disappear, but the Times is long known to want to expand internationally. Until now it has been held back by the Herald.
It has long been known that the Herald has lost money, but was respected both editorially and as an international brand. The paper has been partly kept going by its profitable conferences division, which is believed to offset any losses from the paper.
Peter C Goldmark Jr, chairman and CEO of International Herald Tribune said in a statement: "A change in ownership is intended. But there will be no change whatsoever in our commitment to quality, and independent journalism. That is what we are, that is what we stand for and that is what we shall remain."
He added: "The Washington Post has been a superb and responsible co-owner of the International Herald Tribune. The New York Times is one of the foremost and best newspapers in the world, and we are ready to go forward with them and to continue giving readers the concise, first-rate global reporting and news analysis they depend upon us for."
Reports suggest that the split may not have been amicable. According to a report in the Wall Street Journal, the Post is giving up its stake in the paper reluctantly.
A Post spokeswoman is quoted as saying: "We had hoped to be part of the IHT for many years to come, but under the terms of the deal the New York Times left us little choice. It is impossible to remain a partner with an unwilling partner and we reluctantly agreed to sell."
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