Willey Glover Denis (February 26, 1879 – January 9, 1929) was an American biochemist and physiologist. She was noted particularly for her collaborations with Otto Folin, including studies of protein metabolism. She was a pioneer in the field of clinical chemistry and the measurement of protein in biological fluids (blood, urine and cerebrospinal fluid. She also developed the first reliable method of assaying lead in body tissue and waste.