The Grand Union Canal in England is part of the British canal system. It is the principal navigable waterway between London and the Midlands. Starting in London, one arm runs to Leicester and another ends in Birmingham, with the latter stretching for 137 miles (220 km) with 166 locks from London. The Birmingham line has a number of short branches to places including Slough, Aylesbury, Wendover, and Northampton. The Leicester line has two short arms of its own, to Market Harborough and Welford.

It has links with other canals and navigable waterways, including the River Thames, the Regent's Canal, the River Nene and River Soar, the Oxford Canal, the Stratford-upon-Avon Canal, the Digbeth Branch Canal and the Birmingham and Fazeley Canal.

The canal south of Braunston to the River Thames at Brentford in London is the original Grand Junction Canal. At Braunston the latter met the Oxford Canal linking back to the Thames to the south and to Coventry to the north via the Coventry Canal. "Grand Union Canal" is also the original name for what is now the Leicester line of the modern Grand Union, running from short east of Braunston to Leicester, and which is now sometimes referred to as the Old Grand Union Canal to avoid ambiguity.