Ruy López de Segura was a Spanish priest and chess player born around 1530. He is best known for his influential book, Libro de la invención liberal y arte del juego del ajedrez, published in 1561. This work is one of the earliest comprehensive texts on chess strategy and theory, helping to shape modern chess. López is credited with developing several opening strategies, including the Ruy López opening, which remains popular among players today. His contributions to chess not only advanced the game but also established him as one of the first chess theorists, influencing generations of players and writers.