Petronilla of Chemillé (died 24 April 1149) was the first abbess of the double monastery of Fontevrault in western France, which she headed from 1115 to 1149 following her second widowhood.

After Philippa of Toulouse persuaded her husband, William IX, Duke of Aquitaine, to grant Robert land for the foundation of an abbey, Robert left both Hersende de Champagne and Petronilla in charge of monitoring the construction and organization.

A year before Robert's death, he named Petronilla (by then a widow) as the first abbess of his monastery.

Petronilla commissioned the first biography of Robert of Arbrissel from his friend Baldric of Dol.

The Bollandists remark: "Her existence was marked by many contradictions, but she had the courage to pass beyond the judgment of human beings and to walk without deviating on the path to heaven.