Route 9 is a 135.310-mile-long (217.760 km) major east–west state highway in Massachusetts, United States. Along with U.S. Route 20, Route 2, and Interstate 90, Route 9 is one of the major east–west routes of Massachusetts. The western terminus is near the center of the city of Pittsfield. After winding through the small towns along the passes of the Berkshire Mountains, it crosses the college towns of the Pioneer Valley and then south of the Quabbin Reservoir and the rural areas of western Worcester County. Entering the city of Worcester from the southwestern corner of the city, it passes through the center of the city and forms the major commercial thoroughfare through the MetroWest suburbs of Boston, parallel to the Massachusetts Turnpike. Crossing the Route 128 freeway circling Boston, it passes through the inner suburbs of Newton and Brookline along Boylston Street, and enters Boston on Huntington Avenue, before reaching its eastern terminus at Copley Square.

Route 128, known as the Yankee Division Highway, is an expressway in the U.S. state of Massachusetts maintained by the Highway Division of the Massachusetts Department of Transportation (MassDOT). Spanning 57 miles (92 km), it is one of two beltways around Boston, and is known as the "inner" beltway, especially around areas where it is 15 miles (25 km) or less outside of Boston. The route's current southern terminus is at the junction of I-95 and I-93 in Canton, and it is concurrent with I-95 around Boston for 37.5 miles (60.4 km) before it leaves the interstate and continues on its own in a northeasterly direction towards Cape Ann. The northern terminus lies in Gloucester a few hundred feet from the Atlantic Ocean. All but the northernmost 3 miles are a freeway, with the remainder being an expressway. Its concurrency with I-95 makes up most of its length.