Kahlo was born Magdalena Carmen Frieda Kahlo y Calderón in her parents' house in Coyoacán, which at the time was a small town called Coyoacan on the outskirts of Mexico City. Her father, Guillermo Kahlo (1872-1941), was a German who was born in 1871 in Pforzheim, Germany as Carl Wilhelm Kahlo to Lutheran parents whose antecedents, craftsmen, soldiers, gingerbread bakers and sluice keepers, have been traced back to the 16th century. His father was the jeweler and goldsmith Jakob Heinrich Kahlo and his wife Henriette née Kaufmann, both of whom were ethnic Germans and Lutherans (although some sources incorrectly claim that her father was Jewish[1]). Wilhelm Kahlo sailed to Mexico in 1891 at the age of 19 where he then changed his German forename for its Spanish equivalent, Guillermo. Frida's mother, Matilde Calderón y Gonzalez, was of primarily indigenous descent mixed with Spanish and was a very devout Catholic who frowned upon the wild games that Frida and her younger sister and best friend, Cristina, played. Frida was the product of an unhappy marriage; her father had hastily married her mother after his first wife died in childbirth. For most of her life, Kahlo was closer to her father than to her mother. The young Frida suffered a bout of polio at age six, which left her right leg looking much thinner than the other (a deformity that Kahlo hid by long skirts). Still, with the feisty and brash personality that she kept throughout her life, and with her father's encouragement to participate in boxing and other "manly" sports, she overcame her disability. In 1922, Kahlo was enrolled in the Preparatoria, one of the top schools in Mexico, where she was one of only 35 girls. Kahlo joined a gang at the school and fell passionately in love with the leader, Alejandro Gomez Arias; her first real love affair, but certainly not her last. Kahlo also witnessed violent armed struggles in the streets of Mexico City as the Mexican Revolution took place. It was a moment that changed Kahlo's life.

Kahlo was heavily influenced by the Mexican revolution, which began in 1910 when she was just three. In her writings she recalled that her mother would usher her and her sisters inside as gunfire could be heard in her hometown. Men would leap over the walls into her backyard, and some days her mother would prepare a meal for the starving revolutionaries. In fact, Kahlo went as far as to claim that she was born in 1910 so that people would associate her directly with the revolution.