He was born in Turkey in 1949 to a Turkish rural family. Ocalan studied in Ankara University, where he acquired leftist leanings.
From university, he started his political career supporting the separation of Turkish Kurds, and calling for a separate Kurdish state in south eastern Turkey.
Turkish authorities jailed him in 1972 for seven months. In 1978 he established his Marxist party Kurdistan’s Workers Party (PKK). He left Turkey in 1980 and started an anti-government campaign from exile.
Ocalan founded camps for his PKK fighters in al-Bekaa, Lebanon before he was forced to move to Syria because of Turkish pressure. PKK camps in Lebanon were shut down.
For more than a decade he operated from Syria. In 1998 tension between Syria and Turkey over a water conflict as well as Ocalan reached the point of imminent full-scale war.
Turkey accused Syria of offering Ocalan a base to launch anti-Turkish government attacks.
Ocalan left Syria for Italy, where he sought political asylum. Italy did not grant him asylum, despite the widespread Kurdish protests that swept across Europe in his support.
PKK has always been a military
Ocalan turned up in Kenya, where he took refuge in the Greek Embassy, but on 16 February 1999 a special Turkish commando force seized Ocalan and whisked him back to Turkey.
It is widely believed that the arrest was an international intelligence operation involving several countries. How the Turkish force managed to enter the Greek Embassy in Nairobi and snatch Ocalan remains a mystery.
Ocalan was tried by a Turkish state security court at his prison in the island of Imrali in the Sea of Marmara, and was sentenced to death on 29 June.
Ocalan called on his followers to end their attacks on the Turkish army and government interests and leave Turkey.
The Court of Appeal began reviewing Ocalan's case on 21 October, and on 25 November the court upheld the conviction and the sentence.
The Turkish government agreed to a request that the case be referred to the Court of Human Rights of the Council of Europe in Strasbourg, France, a gesture believed to be motivated by the Turkish desire to become a member of the European Union.