Boulsworth Hill is a large expanse of moorland, the highest point of the South Pennines of south-eastern Lancashire, England, separating the Borough of Pendle from Calderdale.

Its summit, Lad Law, is 1,696 ft (517 m) above sea level, and commands views over Pendle Hill, the Forest of Bowland, the Yorkshire Dales and the South Pennines.

[1] On an exceptionally clear day it is possible to see Scafell Pike and Helvellyn to the north, Ferrybridge power station to the east, High Peak to the south and the Big One roller coaster at Blackpool Pleasure Beach to the west.

[5] The hill is covered by acidic grassland,[6] which provide a valuable breeding ground for red grouse, twite,[5] golden plover[5] and other birds.

It lies just inside Lancashire, although the county boundary with the West Yorkshire district of Calderdale passes just a mile to the southeast of Lad Law.