Hoffman, 46, who won a best actor Oscar for his role in the 2005 biographical film "Capote," was considered to be one of the finest stage and screen actors of his generation.
O'Donnell, known as Mimi, is the mother of the couple's three young children, Cooper, Tallulah and Willa.
She was also named executor of the estate. The exact value of Hoffman's estate is not known.
In the will dated October 2004, the late actor also set up a trust fund for his then only child, Cooper, and requested that he be raised in New York, Chicago or San Francisco. If that was not possible, Hoffman requested that his son visit the U.S. cities at least twice a year.
"The purpose of this request is so that my son will be exposed to the culture, arts and architecture that such cities offer," the will said.
Although Hoffman was found in his Greenwich Village apartment with a syringe in his arm, the cause of his death was still undetermined pending the results of further studies.
Hoffman appeared in quirky independent films and blockbusters such as "The Hunger Games" series, and received best supporting actor Oscar nominations for "The Master," "Doubt" and "Charlie Wilson's War."
On stage, he was nominated for a Tony award for his role as Willy Loman in Arthur Miller's Pulitzer Prize-winning play "Death of a Salesman."