Esmond Emerson Snell (September 22, 1914 – December 9, 2003) was an American biochemist who spent his career researching vitamins and nutritional requirements of bacteria and yeast. He is well known for his study of lactic acid-producing bacteria, developing microbiological assays for a number of key nutrients; the discovery of more than half of known vitamins has been attributed to the use of this work. He discovered several B vitamins, including folic acid, and characterized the biochemistry of vitamin B6 (also known as pyrixodal).