Carlo Raimondo Michelstaedter or Michelstädter (German pronunciation: [ˈmɪçl̩ˌʃtɛtɐ]; 3 June 1887 – 17 October 1910) was an Italian philosopher, artist, and man of letters.

Carlo Michelstaedter was born in Gorizia, the capital of the Austro-Hungarian County of Gorizia and Gradisca, the youngest of four children of Albert and Emma Michelstaedter (née Luzzatto). His full name was Carlo Raimondo (Gedaliah Ram). His father was the director of the local branch of the Trieste-based Assicurazioni Generali insurance company. The Michelstaedters were an Italian-speaking upper middle class Jewish family of Ashkenazi origin.

His sister Paula remembered him as a child fearful of the dark and heights, stubborn and not at all prepared to apologize for any misbehavior. In school, he was judged "not very suitable" for having intentionally and frequently disturbed the lessons during the year.

His father was also the chairman of the Gabinetto di Lettura Goriziano, a local cultural association for the fostering of literary culture, and he pushed his son towards literary study. His mother Emma Luzzatto came from an old and renowned Jewish family of Italian irredentist leanings. His aunt was Carolina Luzzatto, who was also a supporter of Italian irredentism. Carlo was considered an introverted boy, but by the end of high school (completed in Gorizia), he developed into a brilliant, athletic, intelligent youth. He enrolled in the department of mathematics at the University of Vienna, but soon moved to Florence, a city he savored for its arts and language. There he formed friendships with other students, and in the end, enrolled in the department of letters of the local Istituto di Studi Superiori (1905). He majored in Greek and Latin, and selected for his laurea thesis a philosophical study of persuasion and rhetoric in ancient philosophy. In 1909 he returned to Gorizia and set himself to work on the thesis.

Around the fall of 1910, he completed his work, finishing the appendices by 17 October. He was very tired, and that day he had a fight with his mother, who complained he had not wished her a happy birthday. Left alone, Carlo took a loaded pistol he kept in the house and killed himself with two shots. The reasoning behind his suicide has been a subject of much debate; some see it as the natural conclusion to his philosophy, others see it as a result of some kind of mental illness. One of his friends from Florence, a Russian woman, had also killed herself, as had a brother who lived in America. He is buried in the Jewish cemetery in Rožna Dolina near Nova Gorica, Slovenia. As his family was Jewish, they were sent to Auschwitz; only one sister escaped to Switzerland.

Friends and relatives published his works and collected his writings, now in the Biblioteca Civica di Gorizia.

Not only did he write Persuasion and Rhetoric, but many stories, plays and dialogues; thousands of unfinished pages, most of which have been only translated to Spanish.

For Michelstaedter, common life is an absence of life, narrow and deluded as it is by the god of pleasure, which deceives man, promising pleasures and results that are not real, although man thinks they are. Rhetoric—that is, the conventions of the individual, the weak, and society—comprises social life, in which man overpowers nature and himself for his own pleasure. Only by living in the present as if every moment were the last can man free himself from the fear of death, and thus achieve Persuasion; that is, self-possession. Resignation and adapting oneself to the world, for Michelstaedter, is the true death.