Fritz Heinrich Angerstein (January 3, 1891 – November 17, 1925) was a German mass murderer, who killed eight people at his home in Haiger, on December 1, 1924.

The subject of a media spectacle, Angerstein, along with Fritz Haarmann and Peter Kürten, is considered one of the "three great mass murderer trials" of the Weimar Republic-era of Germany.

[2][3] Angerstein suffered from health problems during his childhood, including regular tuberculosis infections and having a rib surgically removed, but at age 14 began working as a surveyor, before being employed by the Nassauische Bergbau AG.

Angerstein related that his mother-in-law often reduced Käthe's diet to soup, due to her ailments, though apparently she often burnt the meal, whereupon his wife would not eat anything at all.

[3] The same year, Angerstein, together with his wife, mother-in-law and sister-in-law, moved to Haiger after he received free lodging in a villa belonging to his employer, van der Zypen.

[citation needed] Angerstein got into financial troubles, whereupon he began to embezzle money from his employer, which according to court records the total sum was 14,892 ℛℳ.

[6] On the Friday before the murders, Angerstein witnessed his wife put away a notebook containing her last wishes, stating she was expecting to die soon.

[3] Startled by six shots during the night in front of the house, his wife began suffering from bloody diarrhea, vomiting, fainting and heart problems due to the agitation.

[3] Angerstein learned the next day that the shots had been fired during a birthday party, and he began to suffer from severe headaches.

He overheard his wife and mother-in-law talking about another letter written by his brother-in-law, stating that he had syphilis, and that the disease could spread to other family members, agitating him.

Finding a hand-axe, he intended to cut off his own hand, but hearing his mother-in-law scream he ran back upstairs and killed her because, as he later claimed, he was angry about her having treated his sick wife badly.

During the course of the day he also killed the son of the villa gardener, Geist, and another laborer working for him, Darr, with a hatchet, fearing that they both might have seen the dead bodies.

[5][11] Source:[14] Out of fear that the public could turn against Angerstein, he was taken to Limburg an der Lahn only two weeks before the trial started in July 1925.

[3] On July 13, after six days of trial, Angerstein was sentenced to death eight times, once for each of the eight murders, and deprived of his civil rights for the rest of his life, while the other charges against him were dismissed.

[16][17][18] On November 17, 1925, at 8 a.m., Angerstein was executed by decapitation with an axe by executioner Carl Gröpler in the courtyard of the Central Prison Freiendiez in Diez an der Lahn.

Rumours circulated to the effect that Angerstein was inspired by the Sixth and Seventh Books of Moses, which state that by killing nine people a seal may be activated that provides great riches.

[7] The case has gained some notoriety for allegedly being one of the rare instances in which an optogram, a photograph taken from a dead person's retina, played a role in identifying and convicting a murderer.