One of the most comprehensive displays of works by Diego Velázquez is opening this week at Paris’s Grand Palais. Showcasing 119 artworks from museums around the globe, it will cover the breadth of his career. But pulling together this large retrospective of the influential 17th-century Spanish painter was no easy feat for curator Guillaume Kientz.

Mr. Kientz, the chief conservationist for Spanish paintings at the Louvre, which is jointly producing the exhibition, spent the past two years negotiating with private collectors and museums to assemble some of the Spanish master’s most famous works in what will be the Grand Palais’s blockbuster show of the year.