Sadamichi Hirasawa (-1987) was a Japanese painter who was sentenced to death accused of mass cyanide poisoning.

On January 26 1948 a man arrived in a branch office of the Teikoku Ginko bank at Shiinamachi , suburb of Tokyo, before closing time. He explained that he was a public health official sent by US occupation authorities who had orders to inoculate the staff against a sudden outbreak of dysentery. The sixteen employees drank the liquid he gave, which was a cyanide solution. When the employees were incapacitated, the robber took all the money he could find, which amounted to only 160,000 yen. Ten of the victims died at the scene and two others in the hospital.

Surviving victims described a scar under the murderer's chin and police investigation lead to Hirawasa through the use of stolen checks. He was arrested August 1948. Hirasawa confessed (though he later retracted the confession) and was sentenced to death. His lawyers argued that the sentence was against the new Japanese constitution. Over the following years they submitted 18 pleas for retrial , but the Supreme Court of Japan upheld the death sentence in 1955.

Hirasawa remained in prison for the next 33 years. He spent his time painting and writing his autobiography. The death sentence was never carried out and he died in prison hospital in 1987.

Even after Hirasawa's death, his stepson Takehiko Hirasawa has tried to clear his name. As of 2004, his lawyers have submitted new pieces of evidence to prove Hirasawa's innocence.