The Grand Canal begins at the River Liffey in Grand Canal Dock and continues through to the River Shannon with various branches, including a link to the River Barrow waterway at Athy.

From Grand Canal Dock it passes through Ringsend and then traverses the southside, deliniating the northern extremities of Ballsbridge, Ranelagh, Rathmines, Harolds Cross and Crumlin. At Inchicore can be seen the path of the original branch to the Guinness brewery and James Street Basin which was filled in the 1970's.

From there the canal heads west through the suburbs of Dublin West and into Kildare. At Sallins the Naas/Corbally branch diverts southwards while the Grand Canal continues west passing Prosperous and Robertstown. Just east of Robertstown is the location where the Blackwood Feeder used to join the canal, whilst just to the west can be found the busiest junction on the canal where the Old Barrow Line, Milltown Feeder and the entrances to the Athy & Barrow Navigation. Further west, the canal passes Edenderry and Tullamore before it reaches the Shannon.