'''Tirozin''' (''Tyr'' ali ''Y'') <ref>{{cite web | author=IUPAC-IUBMB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology
| year = 1983 | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17}}</ref> ali '''4-hidroksifenilalanin''', je ena od 22 [[amino kislina|amin kislinaminokislin]], ki jih [[Celica|celice]] potrebujejo za sintezo [[protein|beljakovin]]. Gre za ne-esencialno aminokislino s polarno stransko skupino. Njena [[kodon]]a sta UAC in UAU. Ime "tirozin" izvira iz [[grščina| grškega]] ''TYROS'', kar pomeni '' [[sir]]'': snov je leta 1846 v [[kazein]]u, beljakovini v sirih, odkril in poimenoval nemški kemik [[Justus von Liebig]]. <ref name="urltyrosine — Infoplease.com">{{cite web | url = http://www.infoplease.com/ce6/sci/A0849873.html | title = Tyrosine | author = | authorlink = | coauthors = | year = 2007 | work = The Columbia Electronic Encyclopedia, 6th ed | publisher = Infoplease.com — Columbia University Press | pages = | archiveurl = | archivedate = | quote = | accessdate = 2008-04-20}}</ref><ref name="urlOnline Etymology Dictionary">{{cite web | url = http://www.etymonline.com/index.php?term=tyrosine | title = Tyrosine | author = Douglas Harper | authorlink = | coauthors = | year = 2001 | work = Online Etymology Dictionary | publisher = | pages = | archiveurl = | archivedate = | quote = | accessdate = 2008-04-20}}</ref>Imenuje se '''tirozil''', kadar je govora o funkcionalni skupini ali stranski verigi. Tirozin je hidrofobna aminokislina.
