The James Bay Road (French: Route de la Baie James), officially the Route Billy-Diamond Highway, is a remote wilderness highway winding its way through the Canadian Shield in northwestern Quebec and reaches into the James Bay region. It starts in Matagami as an extension of Route 109 and ends at Radisson. The road is fully paved, well maintained, and plowed during the winter. It was originally constructed to carry loads of 300 tons, and has mostly gentle curves and hills with wide shoulders. The road is maintained by the Eeyou Istchee James Bay Regional Government (formerly by the municipality of Baie-James). Connecting to other routes such as the Trans-Taiga Road and the Route du Nord, the highway draws tourists interested in reaching the remote wilderness surrounding James Bay, part of Hudson Bay.

On November 10, 2020, the James Bay Road was renamed in honour of Billy Diamond, former Grand Chief of the Grand Council of the Crees and chief Cree negotiator of the James Bay and Northern Quebec Agreement.

There is currently a proposal supported by the region's Cree communities to build a gravel extension some 250 kilometres (160 mi) further north to the twin communities on the Great Whale River - the Cree village of Whapmagoostui and the northern (primarily Inuit) village of Kuujjuarapik, in the Nunavik region.