Lawrence S. Eagleburger, a troubleshooting diplomat and senior foreign policy adviser to presidents who served the country for more than 40 years, including 42 days as secretary of state at the close of President George Bush’s term, died on Saturday in Charlottesville, Va. He was 80.

The cause was pneumonia, according to a spokeswoman for the family, Anaïs Haase, who said he died at the University of Virginia Medical Center after having a heart attack earlier in the week. He lived in Charlottesville, on a 40-acre estate.

Mr. Eagleburger, a Republican who rose to prominence as the top aide to Henry A. Kissinger in the Nixon and Ford administrations, was candid in his confidential advice and outspoken in his public comments, particularly regarding his unhappiness about the Iraq war started by President George W. Bush....