Born Renato Zavagli Ricciardelli delle Caminate in Rimini, Italy, on 4 February 1909, René Gruau was the son of an Italian count but instead of following in his father's footsteps and accepting the job of royal military commander his passion and inclination for arts led him to a love and pursuance of fine arts.
When René's mother, Maria Gruau, a French aristocrat, and his father separated when he was three, he moved to Paris with her. Gruau then took his mother's last name, which is the name he is known by, opposed to his father's last name and noble connection. At 14, Gruau began to support his mother and himself by selling drawings to the Milanese fashion journal Lidel.
He demonstrated talent for drawing throughout much of his early life and worked as an illustrator for fashion magazines such as Femina, Marie Claire and Vogue in Paris in his teens and early 20s. Gruau found it difficult to find work during World War II and ultimately found little work for small or unestablished designers such as Christian Dior before he became popular during this time. He worked as he could and contributed to the concealment of Jewish refugees.