Cedar Bay is a stream in Wayne County in the U.S. state of Missouri. It is a tributary of the Black River. The stream headwaters arise about two miles south of Piedmont (at 37°07′10″N 90°41′01″W / 37.11944°N 90.68361°W) and the stream flows south and then southwest to its confluence with the Black River just north of Leeper (at 37°04′44″N 90°42′47″W / 37.07889°N 90.71306°W) at an altitude of 430 feet (130 m). Missouri Route 34 and Missouri Route 49 run parallel to the stream channel for its entire course.