Willem Leonard Oltmans (addressed as William Oltmans in some English publications; 10 June 1925 – 30 September 2004) was a Dutch investigative journalist and author active in international politics.
Oltmans interviewed and befriended Indonesian president Sukarno in 1956 and began propagating the handover of Western New Guinea (since 1949 the last remaining Dutch overseas territory in Asia) to the Republic of Indonesia to the Dutch public.
Due to this, and the highly critical stance he often took towards Dutch foreign policy in his works, the Dutch government, spearheaded by Minister of Foreign Affairs Joseph Luns, conspired to keep him out of employment. For a long time, Oltmans was forced to live off welfare.
A lengthy lawsuit starting in 1991 and involving the Dutch Royal Household led to the state having to pay him damages. In 2000, he was awarded 8 million guilders (approx. 3.4 million euro) in compensation.
In 2004 Oltmans ended his life through euthanasia after he had been diagnosed with a serious form of cancer.