In the dystopian novel Nineteen Eighty-Four (1949), by George Orwell, the Thought Police (Thinkpol in Newspeak) are the secret police of the superstate of Oceania, who discover and punish thoughtcrime (personal and political thoughts unapproved by Ingsoc's régime). Using criminal psychology and omnipresent surveillance (via informers, telescreens, cameras, and microphones) the Thinkpol monitor the citizens of Oceania and arrest all those who have committed thoughtcrime in challenge to the status quo authority of the Party and of the régime of Big Brother.
Orwell drew inspiration from his observation of the NKVD's methods of surveillance, control, and punishment of dissent in the Soviet Union and from his experiences in the Spanish Civil War.