Mikel Lejarza Eguía (born 1947 in Areatza, Basque country) was a member of the Spanish intelligence service. During the 1970s, he worked undercover as a double agent infiltrating the Basque separatist organisation ETA. The secret service knew him by the nickname El Lobo (The Wolf). Lejarza provided safe houses for ETA in Spain to lodge ETA's commandos.
As a result of Lejarza's long-time operation, a major police operation against ETA took place in 1975, resulting in more than 150 arrests and a number of alleged summary executions by the Guardia Civil. They were considered political prisoners and were released when Juan Carlos I became king some months later.
- Duva, Jesús (5 November 2004). "Entre la traición y la heroicidad". El País (in Spanish) (Madrid: Edicíones El País). Retrieved 11 August 2010.
- Miralles, Melchor (1 November 2004). "Mikel Lejarza, 'Lobo': 'Seré un objetivo de ETA mientras viva'". El Mundo (in Spanish). Madrid: Mundinteractivos, S.A. Retrieved 11 August 2010.
- "27-IX-75: El día en que Franco gastó sus últimas balas". Foro por la Memoria (in Spanish). Retrieved 11 August 2010.
- "The Wolf". World Movies. Retrieved 11 August 2010.
- ""El lobo": "Nunca pude permitirme tener miedo"". Cadena Ser (in Spanish). 28 October 2004. Retrieved 11 August 2010.