Hacker may refer to:

• Computer hacking, including the following types of activity:
  • Hacker (programmer subculture), activity within the computer programmer subculture
  • Hacker (hobbyist), to heavily modify the software or hardware of one's own computer system
  • Hacker (computer security), to access computer networks, legally or otherwise
  • Computer crime
• Illegal taxicab operation
• Pleasure riding, horseback riding for purely recreational purposes
• The act of stealing jokes
• Hacking, an area within Hietzing, a municipal district of Vienna, Austria
• Ian Hacking, Canadian philosopher of science