Peter McLaren Donald Duff FRSE FGS (1927–1998) was a Scottish geologist and academic author.
Duff was born in Edinburgh the son of the personnel officer to the London & North Eastern Railway.
On his return to the University of Edinburgh, he instead decided to study geology, under Professor Arthur Holmes, graduating with a BSc in 1951.
However, it was hard to surpass the original survey work by James Ernest Richey FRSE and Duff abandoned the project.
His proposers were Gordon Y Craig, E Kendall Walton, Sir Frederick H Stewart and Charles Waterston.