What was the name of the Achaemenid royal road connecting Susa with Sardis?

The Achaemenid royal road connecting Susa with Sardis was the Persian Royal Road.

The road crossed much of the Achaemenid Empire, linking Susa in southwestern Iran with Sardis in western Anatolia. Herodotus described its stations, distances, and royal couriers, making it one of the best-known communication routes of the ancient world.

Darius I organized and improved the imperial road system after expanding the empire. Couriers could change horses at staffed stations, allowing official messages to travel far faster than ordinary travelers. Herodotus famously praised the system’s reliability, though his account concerns the courier service rather than every detail of the road’s construction.

The Royal Road was not identical to the later Silk Road, a broad network whose routes and periods varied. Nor was it a single modern-style paved highway throughout. It was an imperial communications corridor with roads, staging posts, guards, and administrative support.