Weir is an outlying area of Bacup in the Rossendale borough of Lancashire, England and is adjacent to the more historically significant Broadclough. Anciently, Weir constituted a hamlet, but underwent urbanisation and, later, suburbanisation to emerge as a residential suburb of Bacup town after the Burnley Road turnpike was built through the settlement in the 18th Century. Weir straddles the A671 road and is located by the source of the River Irwell, adjacent to the parish of Cliviger.