The Grey Stone of Trough is an historic boundary marker in Bowland Forest High, in the Trough of Bowland, Lancashire, England. A Grade II listed structure, erected in 1897 and standing on Trough Road, it marks the line of the pre-1974 county boundary between Lancashire and the West Riding of Yorkshire. Historically, the Trough marked the westernmost boundary of the ancient Lordship of Bowland.

It is in sandstone and has a triangular section with inscriptions on the two sides that face the road.

Inscriptions

Lancashire side

"To Lancaster, 12 miles. Bay Horse, 10 miles"

Yorkshire side

"To Whitewell, 5 miles. Clitheroe, 12.5 miles"

Gallery

• 
  The Yorkshire side of the marker
• 
  The Lancashire side of the marker