The Hartheim Euthanasia Centre (German: NS-Tötungsanstalt Hartheim) was a killing facility involved in the Nazi programme known as Action T4, in which German citizens deemed mentally or physically unfit were systematically killed with poison gas. This was initially a programme of involuntary euthanasia permitted under the law ostensibly to enable the lawful and painless killing of incurably ill patients; these killings continued even after the law was rescinded in 1942 and extended to include Jews, Communists and others considered undesirable by the state. Concentration camp inmates who were unfit for work, or otherwise deemed troublesome, were also executed here. The killing centre was housed in Hartheim Castle in the municipality of Alkoven, near Linz, Austria.