RK may stand for:

  • Radial keratotomy
  • Rajesh Khanna, a Bollywood film actor
  • Reality Kings, a North American porn site
  • Relient K, a Christian rock band
  • Religious knowledge, also known as religious education
  • Riddlin' Kids, a punk rock band from Austin, Texas
  • Rikenium (Rk), a proposed name for Ununtrium
  • Rilo Kiley, an indie rock band from Los Angeles, California
  • Rizzle Kicks, an indie-rap duo from Brighton, UK
  • r/K selection theory, relating to the trade-off between quantity and quality of offspring
  • RK 95 TP or RK 62, Finnish assault rifles (RynnäkköKivääri)
  • Royal Khmer Airlines' IATA airline designator