Grand Union Canal

Grand Union Canal, artificial waterway system, central and southern England, in total running for over 480 km (300 mi). The canal's main line runs for 143 km (89 mi) from its junction with the Thames at Brentford, London, to Norton Junction, north of which it splits to continue for 77 km (48 mi) via the Oxford Canal to Birmingham, and for 125 km (78 mi) via Leicester, Loughborough, the River Soar, and a junction with the River Trent at Long Eaton, to Langley Mill. In addition, the line around London is linked to three other main branches: the Paddington Arm runs from the mainline junction at Bull's Bridge to Paddington Basin, Regent's Canal from Paddington Basin to the Thames at Limehouse, and Hertford Union Canal from Regent's Canal at Bethnal Green to the River Lea at Old Ford Junction. Other minor arms include the Slough, Aylesbury, Northampton, Wendover, Buckingham, and Market Harborough.

The Grand Union Canal was created by an amalgamation in 1929 of the Grand Junction—at 303 km (188 mi) its backbone—and the Regent's, Warwick and Napton, Warwick and Birmingham, and Birmingham and Warwick Junction Canals, to join London and various parts of the Midlands, and form England's biggest canal system. It was constructed by a number of engineers. At Tring, a summit reservoir was needed to supply water to a height of 90 m (296 ft).

Once, a large part of the canal's traffic brought milk and fresh produce into London daily; it also transported various goods from the Midlands to ports in Northern Europe. Today, despite a high concentration of locks, it is almost exclusively populated by pleasure boats. There is some famously beautiful countryside in the Chilterns and Warwickshire, though the north-eastern branch is occasionally highly polluted, for example at Leamington Spa.