Johann Caspar Fuessli, also written Johann Caspar Fuesslins or Fuessly, was a Swiss painter, entomologist and publisher.

He was born in Zurich, the son of Johann Caspar Füssli (1706–1782) and Anna Elisabeth Waser. He was thus the brother of Henry Fuseli (Johann Heinrich Füssli, 1745–1825). He married twice: to Verena Störi in 1770, and Anna Elisabeth Kilchsperger in 1774.

The only spider species he described (as Fuesslin, 1775) is the "daddy long-legs spider", Pholcus phalangioides, also known as "cellar spider".

He died, aged 43, in Winterthur.