This is an abridged version of a BBC report:
The Guardian's current editor Katharine Viner said he was a "brilliant editor" and a "supportive friend".
His son Ben, executive editor of the Sunday Times, said his father "died a good death" and "he was loved" until the end.
Preston first joined the Guardian in 1963, after training at the Liverpool Daily Post. His final column, published on New Year's Eve, focused on the challenges facing journalists "and their rough trade" in 2018.
He became the editor of the paper in 1975 and over the next two decades oversaw a number of exclusive stories about politicians' conduct.
Investigative journalism into defence procurement minister Jonathan Aitken led to allegations that he took bribes from Saudi arms dealers, which resulted in the Conservative MP's eventual imprisonment.
Preston, who was born in Leicestershire, turned his hand to fiction writing after leaving the editorship in 1995.
Piers Morgan, who began editing the News of the World while Preston was still editor of the Guardian, paid tribute to his peer.
He said it was "very sad news" and added he "respected his incisive opinions".
"[He was] a Fleet Street giant and lovely man who will be greatly missed by the newspaper industry."
New Statesman editor Jason Cowley said the 79-year-old was "an excellent and innovative editor who loved our trade".
Alan Rusbridger, Preston's successor at the Guardian, highlighted how he "worked tirelessly for journalists abroad".
Preston, who worked as a foreign correspondent, wrote about the 65 journalists who were killed in 2017, in their home countries and abroad, in one of his final columns for the Observer.
In his column, he referred to Maltese journalist Daphne Caruana Galizia, who was killed by a car bomb in November.
Referring to the 10 female journalists who were killed last year, he said: "Despite threats, they continued to investigate and expose cases of corruption."
Links / further reading: Peter Preston Obituary in The Guardian