Route 121 is a mostly East/West provincial highway in the Canadian province of New Brunswick. The road runs from Route 2 and Route 165 intersection in Dow Settlement. The road has a length of approximately 44 kilometers, and services small, otherwise isolated rural communities. In these areas, the highway is often unofficially referred to as "Main Street." The road bypasses several Lakes including Skiff Lake, Mud Lake, Eel River Lake, North Lake and finally Grand Lake before changing to Boundary Road in Orient, Maine at the Canada–United States border. The Highway is known as Canterbury Road between Meductic and Canterbury.