Denis Patrick O'Brien, FBA (born 1939 in Knebworth, Hertfordshire, England, and died in 2023) was an English economist who worked in industrial economics and the history of economic thought.
O'Brien graduated in 1960 with a BSc (Economics) from University College London. From 1963 to 1972 he was Assistant Lecturer, Lecturer and then Reader in Economics at Queen's University Belfast. From 1972 to 1997 he was Professor of Economics at the University of Durham where he was Emeritus until his death in 2023.