The River Trent is one of the major rivers of England. Its source is in Staffordshire between Biddulph and Mow Cop. It flows through the Midlands (forming a once-significant boundary between the North and South of England) until it joins the River Ouse at Trent Falls to form the Humber Estuary, which empties into the North Sea below Hull and Immingham. The name "Trent" comes from a Celtic word possibly meaning "strongly flooding". More specifically, the name may be a contraction of two Celtic words, tros ("over") and hynt ("way"). This may indeed indicate a river that is prone to flooding. However, a more likely explanation may be that it was considered to be a river that could be crossed principally by means of fords, i.e. the river flowed over major road routes. This may explain the presence of the Celtic element rid (c.f. Welsh rhyd, "ford") in various placenames along the Trent, such as Hill Ridware, as well as the Saxon derived ford. Another translation is given as "the trespasser", referring to the waters flooding over the land.

The Trent historically marked the boundary between Northern England and Southern England. For example the administration of Royal Forests was different north or south of the river, and the jurisdiction of the medieval Council of the North started at the Trent. Although the rise of the identity of the "Midlands" has moved the boundary slightly (the modern idea of the "North" now usually starts at the boundary of Yorkshire) some slight traces of the old division do remain : the Trent marks the boundary between the provinces of two English Kings of Arms, Norroy and Clarenceux - and, although little heard these days, the phrase "born North of the Trent" is one means of expressing that someone hails from the North of England.

It is unusual amongst English rivers in that it flows north (for the second half of its route), and is also unusual in exhibiting a tidal bore, the "Aegir". The area drained by the river includes most of the northern Midlands.

At certain times of the year, the lower tidal reaches of the Trent experience a moderately large tidal bore (up to five feet (1.5 M) high), commonly known as the Trent Aegir; taking its name from the Norse god of the ocean. The Aegir occurs when a high spring tide meets the downstream flow of the river, the funnel shape of the river mouth exaggerates this effect, causing a large wave to travel upstream as far as Gainsborough, Lincolnshire, and sometimes beyond. The aegir cannot travel much beyond Gainsborough as the shape of the river reduces the aegir to little more than a ripple, and weirs north of Newark-on-Trent, Nottinghamshire stop its path completely.