Mahmut Yıldırım (born 1951, Yenidal, Solhan, Bingöl Province), better known as Yeşil (Turkish for "Green"), is a Turkish contract killer. He is wanted for the murders of eight people in Turkey. Among the murders he is accused of is that of Cem Ersever in 1993. Yıldırım, who also used the alias Ahmet Demir, disappeared in 1998 and was the subject of an Interpol Red Notice in 1999. In 2013, security officer Korkut Eken told prosecutors that Yıldırım was still alive.
According to former National Intelligence Organization (MİT) official Mehmet Eymür (speaking in 2011), Yeşil at one time worked for the MİT in Elazığ, but was later let go as he was "out of control." Eymür said that Yeşil later worked with the Turkish Gendarmerie's shadowy JİTEM unit until 1995, and "was given identification cards. Some of his cards even included the title of the 'Prime Ministry Intelligence'.". Eymür said that by 1995 Yeşil had again become too "out of control" and was moved to Ankara, where he was introduced to Eymür (then head of the MİT's Counter-Terrorism Department), with Eymür unaware of Yeşil's status as a wanted criminal. Eymür said he used Yeşil in several operations, but only outside Turkey, and that he was never formally an agent. In 2012, the MİT told prosecutors (in a document leaked to the press) that it had used Yıldırım in four operations, including the one which captured Kurdistan Workers' Party (PKK) commander Şemdin Sakık in 1998. MIT later denied that Yıldırım was an MİT agent, and said it had never used Yıldırım inside Turkey.