New Brunswick Route 420

Route 420 is a 35-kilometre (22 mi) long mostly east–west secondary highway in the northwest portion of New Brunswick, Canada.

The route's eastern terminus starts on Route 108 between the community of McGraw Brook and . The road travels north before turning north-easterly following the South Bank of the Little Southwest Miramichi River through the mostly treed area to the community of . The road continues north east to the community of then passing by the community of .

The road continues north east passing to the community of Sillikers. Continuing the road passes , , then before coming to the intersection of Route 425 near Sunny Corner. The road continues to follow the Northwest Miramichi River through the Metepenagiag Mi'kmaq Nation through the Reserve of Red Bank, passing the northern exit of Route 415, passing the community of Cassilis, passing and the community of South Esk before ending at the community of near Miramichi at the intersection at Route 8 and Route 108.