Rassau, sometimes The Rassau , is a village located in the historic county of Brecknockshire ( Breconshire) and the preserved county of Gwent. It currently lies on the northern edge of the county borough of Blaenau Gwent in Wales. According to the 2011 census, the population of Rassau is 3,234. Residents often refer to either Old Rassau and New Rassau or Bottom Rassau and Top Rassau to distinguish the different parts of the village.
Rassau was originally a part of Beaufort and therefore part of the historic county of Brecknockshire (Breconshire). In 1888 it was transferred, together with a number of other industrialized areas, to the historic county of Monmouthshire (not co-extensive with the modern county of the same name). The postal address of 6 Tramroad Side, for example, would then have been "6 Tramroad Side, Rassau, Beaufort, Monmouthshire". Note that Ebbw Vale was not part of the address as Rassau and Beaufort are on the other side of the river Ebbw – a distinction often ignored today.