Henriette Caillaux was born on December 5, 1874, in Rueil-Malmaison, France. Her birth name was Henriette Raynouard. She grew up in a comfortable environment, and her family life shaped her early years.

At the age of 19, Henriette married Léo Claretie, a writer who was twelve years older than her. The couple had two children during their marriage. However, their relationship faced challenges, and by 1907, Henriette began an affair with Joseph Caillaux while both were still married to other people.

Henriette divorced Léo Claretie in 1908. Joseph Caillaux also went through a difficult divorce journey, but the couple eventually married in October 1911. Henriette expressed that she found "the most complete happiness" in her second marriage. The couple was quite wealthy, with joint assets worth about 1.5 million francs. 

On the evening of March 16, 1914, Henriette Caillaux entered the offices of Le Figaro, asking to see Gaston Calmette, the newspaper's editor. When informed he was not present, she waited in the office until he arrived around 6 p.m. Upon his arrival, she asked if he knew the reason for her visit. Before he could respond, she fired six shots from a Browning automatic pistol at him, hitting him in the abdomen.

After the shooting, Henriette did not try to flee. Workers from nearby offices quickly restrained her and called for a doctor and the police. She demanded not to be touched and expressed her belief that "there is no longer any justice in France." When the police were ready to transport her to headquarters, she insisted on riding in her own car, which the authorities allowed. She was officially charged when she reached the police station. Gaston Calmette succumbed to his injuries six hours later.

Henriette Caillaux's trial began on July 20, 1914, at the Paris Cour d'assises. The case received notable media attention, focusing on the personal and political implications of the murder. Opinions about the case were deeply divided. Some believed she acted out of temporary insanity due to character attacks on her husband, while others viewed her as a calculated assassin, silencing a critic.

The trial attracted significant public interest, even surpassing news regarding the imminent outbreak of World War I. High-profile individuals, including the President of France, Raymond Poincaré, testified during the trial. The defense painted Henriette as a victim of powerful emotions, arguing she lost control over her actions. On July 28, 1914, she was acquitted, as the jury found extremely extenuating circumstances in her case.

After her trial, Henriette Caillaux pursued interests in art, eventually publishing a book about the sculptor Jules Dalou in 1935.