Hieronymus Francken the Younger or Hieronymus II was a Flemish painter and one of the most prominent members of the large Francken family of artists. Along with his brother Frans Francken II he played an important role in the development of new genres in Flemish art in the early 17th century.

Hieronymus Francken II was the son of Elisabeth Mertens and Frans Francken the Elder. His father was a painter born in Herentals who had moved with his painter father to Antwerp. There he had become one of the principal painters during the Counter-Reformation. Hieronymus had three brothers who were painters: Thomas, Frans II and Ambrosius II.

Hieronymus received his first training from his father. He was entered into the books (liggeren) of the Antwerp Guild of Saint Luke in 1605 as a pupil of his uncle Ambrosius. Ambrosius Francken I had trained with Frans Floris and had worked some time in Fontainebleau. In 1607 Hieronymus Francken II was formally admitted as a master of the Antwerp Guild.

In 1609 he likely spent time in Paris, where like his brother Frans II, he may have studied under his uncle Hieronymus Francken I. Hieronymus Francken I worked most of his career in Paris and Fontainebleau and was a court painter to the French court from 1594.

Hieronymus Francken II returned to Antwerp where he spent the rest of his career. From 1616/17 he worked as "ionckmann" (bachelor) in the house of his father Frans Francken I (1542-1616).