Tondu (Welsh for black sward) is a small town near Bridgend in south Wales.

Tondu lies on the A4063 from Bridgend to Maesteg, and was established in the late 18th century as a mining village servicing the Parc Slip colliery . In later years, an iron works was also established, and in the 19th century, a brick works was constructed using the clay from the Carboniferous coal measures to make a variety of bricks, mostly for engineering. The brick works was eventually demolished in 1977. The association with the coal industry was also reflected in the large area office of the National Coal Board in the town and a centre for the Mines Rescue Service . Parc Slip colliery was opened by the Llynfi, Tondu and Ogmore Coal and Iron company , which becameNorth's Navigation Colliery Company Ltd. in 1899. On the day of the annual St. Mary Hill Fair , August 26 1892, a huge explosion shook the mine; 112 men and boys died with 39 surviving, some remained trapped underground for a week before being rescued. Sixty women were widowed and 153 children left fatherless. The mine closed in 1904. A memorial to the disaster still stands consisting of 112 stones - one for every death. Much later, the coal seams were re-worked as part of the Parc Slip opencast coal mine.

The town was traversed by two railway lines, one of which was closed in the 1960s, the remaining line remains open and provides a service from Maesteg to Bridgend and Cardiff.

The River Llynfi flows alongside Tondu on its way to its confluence with the River Ogmore. The Llynfi at this point has had a history of severe pollution. Historically, the pollution started with the coal industry. The coal seams in this part of the south Wales valleys are quite wet and the coal itself is rich in pyrites and thus also rich in sulphur. Such mine waters have a very high burden of coal and rock solids and also contain heavy metals such as nickel, iron and copper in acidic solution. In the 20th century, with the introduction of coal washeries, the mine waters became very rich in fine rock solids. The river also takes away the sewage from Maesteg, originally as crude sewage and then later as treated sewage in a treatment plant that was severely overloaded for much of its life. The establishment of a large paper mill and a cosmetics factory in the 20th century only added to the pollution load. As a result, the people of Tondu became inured to a river in their presence which was visibly very polluted and even changed colour as different types of paper were manufactured at the paper mill, and which also smelled strangely: a mixture of perfumes from the cosmetics factory and sewage from Maesteg.

Tondu is now rapidly becoming a dormitory suburb of Bridgend. It has lost its primary school and its identity as a separate small town is eroding away.