Tuncay Güney (pronounced ['tund?aj '?yne?]; born 25 August 1972 in Kargi), code name "Ipek" (silk), is a Turkish citizen of Dönmeh Jewish origin who claims to have infiltrated the Turkish Gendarmerie's intelligence organization JITEM, Ergenekon, the Workers' Party, and the Gülen movement before being outed.
He is subordinate to Mehmet Eymür, who was discharged from the National Intelligence Organization (Turkish: Millî Istihbarat Teskilâti, MIT).
The information Güney has gleaned on these organizations make him a key figure in the ongoing Ergenekon investigation.
His statements form the backbone of the 2455-page Ergenekon indictment, which mentions him 492 times and labels him a suspect at large (Turkish: firari süpheli).