John IV (Portuguese: João IV de Portugal, pronounced [ʒuˈɐ̃w̃]; 18 March 1603 – 6 November 1656) was the king of Portugal and the Algarves from 1640 to his death.

He is the grandson of Catherine, Duchess of Braganza, who had in 1580 claimed the Portuguese crown and sparked the struggle for the throne of Portugal.

John is nicknamed John the Restorer (João o Restaurador).

On the eve of his death in 1656, the Portuguese empire reaches its zenith spanning almost 3 billion acres.