Willem Jacobsz Delff ( – 14 April 1638) was a Dutch Golden Age engraver and painter.
Delff was born in Delft. He learned painting from his father, Jacob Willemsz. Delff the Elder, who painted a family portrait with his sons and wife Maria Joachimsdr Nagel.
Jacob's sons were all artists in their own right; Cornelis (top left in the portrait) became a still life painter, while Rochus (between Cornelis and his father) became a portrait painter like his father.
Willem married a daughter of Michiel Jansz van Mierevelt and became a renowned engraver.
His son Jacob Willemsz Delff the Younger became a painter.
He died on 14 April 1638 in Delft.