Peter William Barlow (1809-19 May 1885) was an English civil engineer particularly associated with bridges (he designed the first Lambeth Bridge, a crossing of the River Thames in London), the design of tunnels and the development of tunnelling techniques.

He was the son of an engineer and mathematician, professor Peter Barlow of the Royal Military Academy in Woolwich, south-east London. His brother William Henry Barlow was a noted 19th century railway engineer.

While designing the piers of Lambeth Bridge (a suspension bridge design since replaced by the current structure) in 1862, Peter W. Barlow experimented with driving iron cylinders into the clay upon which much of central and north London sits. It was this experience that prepared him to work with James Henry Greathead on the development of a tunnelling shield to dig the Tower Subway in 1870.