Quarterbridge Road (Manx: The Quarters or Quarter Dub – quarterlands of Ballabrooie and Ballaquayle) is situated adjacent to the 1st Milestone road-side marker measured from the startline at TT Grandstand used for the Snaefell Mountain Course on the primary A2 Ramsey to Douglas road in the town of Douglas, Isle of Man.
The Quarterbridge Road runs from the bottom of Bray Hill to the major road junction at the Quarterbridge, where it meets the primary A1 Douglas to Peel road and the A5 Douglas to Port Erin road. The A2 Quarterbridge Road also has minor side-road junctions in the residential outskirts of Douglas town.
The start of Quarterbridge Road is the site of the area which famously became known as Ago's Leap, after motorsport photographer, the late B.R. 'Nick' Nicholls, took a photograph of motorcycle racer Giacomo Agostini wheelying during the 1970 TT Senior race riding his MV Agusta.
The A2 Quarterbridge Road was part of the Highland Course and Four Inch Course used for the Gordon Bennett Trial and Tourist Trophy car races between 1904 and 1922. For the 1906 Tourist Trophy car race, the start was moved from the Quarterbridge/A5 New Castletown Road to the Quarterbridge Road/Alexander Drive road junction adjacent to a property called 'Woodlands' in Douglas town.