John IV, King of Portugal [ João IV] (b Villa-Viøsa, 1603; d Lisbon, 1656). Patron of music and composer of church music such as well-known Crux fidelis. Wrote defence of ‘modern music’ 1649. His magnificent library of church mus. was destroyed in Lisbon earthquake 1755.

John IV (1605–56) King of Portugal (1640–56). As Duke of Braganza, he was a leader of the Portuguese revolt against Spanish rule (1640) and afterwards became king. Portuguese independence was confirmed by victory at Montijo (1644).