The Baker Branch Saint John River is a 48.0-mile-long (77.2 km) river in Maine. The Baker Stream originates in Upper First Saint John Pond (46°01′50″N69°58′56″W) northeast of Truesdale Mountain in the northwest corner of Maine Township 4, Range 17, WELS. The stream flows sequentially through Lower First Saint John Pond, Second Saint John Pond, and Third Saint John Pond before entering T.5 R.17, WELS, to flow into Fourth Saint John Pond. The outflow of 4th St. John Pond (46°04′00″N69°54′26″W) now the Baker Branch, flows into Fifth Saint John Pond on the boundary with T.6 R.17, WELS. In 1939, Fifth Saint John Pond was impounded in T.6 R.17 to form a diversion into the North Branch Penobscot River, but most flow follows the original channel north to Baker Lake at the confluence with Sweeney Brook in T.7 R.17, WELS.