Amsterdam banker.

His firm, Jean de Neufville & fils, unsuccessfully attempted to raise funds for the Americans in the Netherlands.

As representative of the Amsterdam city fathers, met in Frankfurt with William Lee, American commissioner designate to Prussia and the Holy Roman Empire (1778).

Acting without authority, the two men secretly drafted a treaty of amity and commerce between the United States and the Netherlands. When the treaty was revealed (1780), it gave Britain an excuse to go to war with the Netherlands.