NK

NK my refer to

 Businesses 

 Spirit Airlines

 Places 

 Nagorno-Karabakh Republic a de facto state in the Nagorno-Karabakh region
 Nikšić Montenegro (license plate code NK)
 North Korea a common name for the Democratic People's Republic of Korea (DPRK)

 Other uses 

 Natural killer cell , in medicine
 Neue Kerze aka new candle, an old photometric unit of luminous intensity
 NK, nogomentni klub, a Football team in Croatian and Slovenian (e. g. (N.K. Osijek), NK Maribor