照三归知又称照三归端，为黄侃所提出之古代汉语音韵学规律。即中古汉语的照系三等.mw-parser-output .IPA{font-family:"Charis SIL","Doulos SIL","Linux Libertine","Segoe UI","Lucida Sans Unicode","Code2000","Gentium","Gentium Alternative","TITUS Cyberbit Basic","Arial Unicode MS","IPAPANNEW","Chrysanthi Unicode","GentiumAlt","Bitstream Vera","Bitstream Cyberbit","Hiragino Kaku Gothic Pro","Lucida Grande",sans-serif;text-decoration:none!important}.mw-parser-output .IPA a:link,.mw-parser-output .IPA a:visited{text-decoration:none!important}、、、、，上古归于知组（端组），即舌音、、、。

照三归知并未像照二归精那那样得到普遍认同。其原因在于照三组字音来源复杂，并非都来自知组（端组），如“枢，昌朱切”“杵，疑古切”，都是中古照三组字，而枢从区得声，杵从午得声，区、午都是见组字。