Hillsboro Gap, also known as the Gap in the Short Hill is a water gap in the Short Hill Mountain formed by the North Fork of the Catoctin Creek in Loudoun County, Virginia.

Virginia State Route 9 passes through the gap in the town.

In colonial times the main road between Alexandria and Winchester, Vestal's Gap Road, passed through the gap.

That road eventually became the Charles Town Pike and modern day Route 9.

The gap poses a barrier to any widening of Route 9 as the historic town completely fills the gap.