Cedric Henry Reid Thornberry (22 June 1936 – 6 May 2014) was a Northern Irish international lawyer and Assistant-Secretary-General of the United Nations, for which he worked for 17 years.

He spent most of his United Nations service in international peace keeping in Cyprus, the Middle East, the former Yugoslavia and Somalia.

During UNTAG, he was the Director of the Office of the Special Representative of the Secretary-General in Namibia, Martti Ahtisaari, and responsible for co-ordination of the Mission’s day-to-day political operation.

Thornberry also served as the Senior Political and Legal Adviser to UNFICYP and to UNTSO, and was Director of Administration and Management at UN headquarters for four years.

Thornberry was a consultant to NATO in the exercises it conducts with the Partnership for Peace countries and a visiting professor at King's College in London.