Nicholson reported on the fall of Saigon in 1975, the Falklands War, the Balkans conflict, the Gulf War and the 2003 invasion of Iraq.
He joined ITN in 1964 and was the network's senior foreign correspondent between 1989 and 1999.
He died while on a cruise with his wife Diana. ITN chief executive John Hardie said he was a "true legend".
Nicholson, who died on 11 December, presented reports from around the world on ITV's flagship current affairs programme Tonight.
He had four children and three grandchildren.
He was known for smuggling an orphaned girl out of Sarajevo while reporting on the conflict - and bringing her back to the UK, where he adopted her.
The correspondent met nine-year-old Natasha Mihaljcic while he was working on a story about children being trapped by shelling in the Bosnian capital in 1992.
He went on to write a book about the events which was used as the inspiration for the 1997 film Welcome To Sarajevo.
Nicholson was ITN's first bureau chief in South Africa in 1976 and was the first television correspondent to live in the country during apartheid.
He also witnessed the toppling of Saddam Hussein's statue in Baghdad in 2003.
Former ITN presenter Sir Trevor McDonald said Nicholson "was almost without doubt the finest television journalist of his generation".
"His aggressive pursuit of stories came to symbolise what the new kid on the block, as ITN then was, was all about."
ITV News presenter Alastair Stewart said he was "deeply saddened to learn of the death of ITN giant Mike Nicholson".
Mr Hardie said: "Michael Nicholson is rightly regarded as a true legend of ITN.
"As a journalist he is renowned and revered throughout our industry and beyond for his courage, his intelligence, and his compassion."
In a statement, his family described him as "an amazing father, devoted grandfather, loving husband and dear friend".
Veteran ITN war correspondent Michael Nicholson, whose career spanned more than five decades, has died aged 79.