'''Pilek''', (Jawa Kuno: ''pilêg'') biasa juga dikenal sebagai '''nasofaringitis''', '''rinofaringitis''', '''koriza akut''', atau '''selesma''', merupakan [[penyakit menular]] yang disebabkan [[virus]] pada [[sistem pernapasan]] yang terutama menyerang [[hidung]].<ref name=CE11>{{cite journal | last = Arroll |first = B | title = Common cold | journal = Clinical evidence | volume = 2011 | issue = 3 | page = 1510 | date = March 2011 | pmid = 21406124 | doi = | pmc = 3275147|quote=Common colds are defined as upper respiratory tract infections that affect the predominantly nasal part of the respiratory mucosa }} {{open access}}</ref> [[Tenggorokan]], [[Sinus paranasal|sinus]], dan [[laring|kotak suara]] juga dapat terpengaruh.<ref name=CMAJ2014/> Tanda dan gejala mungkin muncul kurang dari dua hari setelah paparan.<ref name=CMAJ2014>{{cite journal|last1=Allan|first1=GM|last2=Arroll|first2=B|title=Prevention and treatment of the common cold: making sense of the evidence.|journal=CMAJ : Canadian Medical Association |date=18 February 2014|volume=186|issue=3|pages=190–9|pmid=24468694|doi=10.1503/cmaj.121442|pmc=3928210}}</ref> Itu termasuk [[batuk]], [[sakit tenggorokan]], [[rhinorrhea]], [[bersin]], sakit kepala, dan [[demam]].<ref name=CDC2015/><ref name=Eccles2005>{{cite journal | author = Eccles R | title = Understanding the symptoms of the common cold and influenza | journal = Lancet Infect Dis | volume = 5 | issue = 11 | pages = 718–25 | date = November 2005 | pmid = 16253889 | doi = 10.1016/S1473-3099(05)70270-X }}</ref> Orang biasanya sembuh dalam tujuh sampai sepuluh hari.<ref name=CDC2015/> Beberapa gejala dapat berlangsung hingga tiga minggu.<ref name=Heik2003>{{cite journal |vauthors=Heikkinen T, Järvinen A | title = The common cold | journal = Lancet | volume = 361 | issue = 9351 | pages = 51–9 | date = January 2003 | pmid = 12517470 | doi = 10.1016/S0140-6736(03)12162-9 }}</ref> Pada orang-orang dengan masalah kesehatan lainnya, [[pneumonia]] kadang-kadang berkembang.<ref name=CDC2015/>
