Leith Valley is a suburb, valley, and general area of the New Zealand city of Dunedin, located to the northwest of the city centre. To differentiate the name of the valley from that of the suburb, the former is usually referred to as the Leith Valley, the latter simply as Leith Valley.
As its name suggests, it is the valley of the Water of Leith, a 14-kilometre (8.7 mi) long stream which flows from the slopes of Mount Cargill south through the northern suburbs of Dunedin. The valley starts close to a saddle, Pigeon Flat, between it and the valley of the Waitati River, which is crossed by the Dunedin Northern Motorway. The motorway follows the flank of Mount Cargill's spur Pine Hill, which forms the northern boundary of the valley. The southern boundary is formed by Maori Hill, the northernmost part of a long ridge which forms a crescent around central Dunedin, culminating at Lookout Point in the city's southwest.
The valley starts steeply in bush-clad countryside, before widening into a narrow flood plain occupied by the start of Dunedin's suburban area. The valley widens, and is hemmed in by steep slopes and occasional cliff faces before joining the northern end of the wide plain which is the location of Dunedin's CBD some 2 kilometres (1.2 mi) from the coast. At its mouth, the valley is some 400 metres (1,300 ft) in width.
Much of Dunedin's water supply comes from reservoirs in the upper reaches of the Leith Valley. These include Ross Creek Reservoir, the oldest reservoir still in active use in New Zealand, and Sullivans Dam. Numerous popular walking tracks traverse the bush-clad reserve land surrounding this reservoir.
The term "Leith Valley" can be used to refer to the semi-rural settlement which lies in the upper reaches of the valley, or - more generally - for both this community and the two suburbs which lie in the lower valley, Glenleith and Woodhaugh.