In the history of gardening and landscaping, a canal is a relatively large piece of water that has a very regular shape, usually long, thin and rectangular. The peak period for garden canals was the 17th and 18th centuries, by the end of which less formal water features were in favour, in the style of the English landscape garden. It is distinguished from a garden pond or lake by its shape, and typically falls somewhere between the two in area. It might be wholly artificial, created by diverting and damming a stream, or based around a natural water feature which is landscaped. Usually it appears to be enclosed, though in fact water passes in and out by channels below the surface. The edges are often walled, and the water relatively shallow.

Traditionally, in England the canal has been associated with the Dutch garden style of the later 17th century, especially from about 1690 to 1720, though this has been challenged in recent years. There was also a tradition of canals in the French formal garden style, culminating in the huge four-armed Grand Canal that dominates the bottom of the Gardens of Versailles, made in 1662–68, the main branch 1585 metres long and 122 wide.

A detailed study of canals in Suffolk found evidence of 56 in the county, some previously thought to be fragments of a moat or "mere ponds"; "Amazingly, in view of the received wisdom about the scarcity of surviving canals nationally, a high proportion of these are still recognisable and water-filled". Analysis of the proportions of these showed that nearly half were between 5 and 10 times as long as they were wide, with the next largest groups (10 or 11 each) those with ratios of 1 to 5, and then 10 to 15. Most were between 50 and 100 metres long, but two were 460 and 300 metres. A few use a tapering shape to give (from one end) an impression of being longer than they actually are. Some had or have islands, others cascades into them.

Apart from being a highly prestigious, because expensive, ornament to a garden, and a pleasant place to walk, canals had some practical uses. A large stock of water near the house may have been useful for watering the garden and other household purposes; some houses had special "dipping pools" for the gardeners and servants to take water from. Many canals were stocked with fish, and they attracted edible waterfowl, who could nest safely if there was an island. Boats of an appropriate size could be taken out, and the Earl of Bristol nearly drowned at Ickworth House in 1717, when he was in "imminent danger from being some time under water in my new-made canal here, with the boate (out of which I fell topsy-turvy) driven by the wind over my head". He may have been fishing with a rod, by now a popular leisure activity. Louis XIV famously staged mock naval battles on the Grand Canal at Versailles. Canals were made during the Little Ice Age, and allowed ice skating during the winter, as well as swimming in summer.

Connections to the very long history of long and thin formal water features in gardens elsewhere have not been clearly demonstrated. Setting ancient gardens aside, these have been a strong feature of the Persian garden and Islamic gardens generally, with some found in Islamic Spain. The very small example in the Generalife, part of the Alhambra, Granada, Spain, is famous. In France, there were examples at Fleury-en-Bière, not far from Paris, in the 16th century, and at the nearby Palace of Fontainebleau by 1609. Numerous others can be seen in the prints of great houses in France by Jacques I Androuet du Cerceau (d. 1584). The medieval garden in England, as elsewhere in Europe, had a long tradition of moats, fishponds, and "decorative meres".

A "canal-like feature" was created for Baptist Hicks, 1st Viscount Campden at Chipping Campden before 1629, but the English history of the garden canal really begins with the English Restoration of 1660, when Charles II and his loyal courtiers returned from an exile mostly spent in the Netherlands, or in France. Although not especially interested in gardens, Charles asked Louis XIV to allow him to borrow his chief gardener and landscaper, André Le Nôtre, apparently to advise on Hampton Court Palace and the planned palace at Greenwich in particular. Permission was given, but Le Nôtre never made the journey, and André Mollet and his brother Claude came instead. André Mollet had worked for both of Charles' parents, and had paid visits to England since the 1620s.

The Mollets were responsible for a canal in what is now St James's Park in Westminster, and the large "Long Canal" (now usually "Long Water") at Hampton Court; the "first long canals to be built in England". Of these, the very long and thin canal (775-metre by 38-metre, or 850 by 42-yards) in St James's was later expanded and remodelled into the current lake, with some filled in to allow for an expansion of Horse Guard's Parade. This was mostly done by John Nash in the 1820s for the Prince Regent. The Hampton Court one remains intact, with a narrow semi-circle added at the palace end by William III in 1699. William III was interested in gardening, and is usually credited with adding to the influence of Dutch gardens on England.

Others soon followed the royal lead, for example at Wrest Park in Bedfordshire, where the "Long Water", "Broad Water" and "Ladies Lake" have managed to survive a makeover by Capability Brown in the 18th century. Wrest Park was done by George London and his partner Henry Wise, the leading English designers of the day, for Henry Grey, 1st Duke of Kent in the 1700s.