This article is about the Class III road numbered C165 maintained by Hertfordshire Council. For other roads numbered C165, see C165.
The C165 is an class III road in Royston. It is the route of the pre-bypass A505.
The road commences at a roundabout with the A505 west of Royston, and passes through an area of heathland, before entering the town centre. Here it meets with the C167 (former A14) and A10. From here, it passes through a mainly residential area to the east of the town centre, before ending up on a T junction with the A505.
The road once marked the boundary between Hertfordshire and Cambridgeshire; however, the local authority boundary was moved north to follow the line of the bypass, ensuring that the town of Royston was managed by a single local authority.