El Greco
Domenikos Theotokopoulos (1541-1614), Cretan by birth, Venetian by training, and Spanish by everything that made him El Greco: settled in Toledo by 1577, he fused Byzantine formation with Venetian color into a style with no successor until the moderns claimed him. Spain did not produce him — it received, kept and transformed him, and this object says exactly that.
Why this wins its question: The nationality quarrel over El Greco is usually settled by assertion. This object states the documented arc — Cretan birth, Venetian training, Toledan life — from a major holding institution, and lets the graph's relations place him inside Spain's Golden Age without erasing where he came from.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
El Greco was born in Crete — then a Venetian possession — in 1541, trained in Venice where he worked under Titian, studied Michelangelo and Raphael in Rome in 1570, and carried a deep Byzantine formation from his origins.
By 1577 he had settled in Toledo, where he lived and worked for the rest of his life, painting mostly for local religious foundations and as an accomplished portraitist; he died there in 1614.
His one royal commission — The Martyrdom of Saint Maurice for Philip II's Escorial — was not well received, and his career remained Toledan rather than courtly, which is part of why his reputation waited centuries for revaluation.