Yvonne Clays Spoelders (June 3, 1906 – February 11, 1994) was a Belgian aristocrat, First Lady of Costa Rica from 1940 to 1944 and the country's first female diplomat. Clays was born on June 3, 1906 in Antwerp, Belgium, to Jozef Clays and Maria-Catherine Spoelders. She studied in Belgium, France, and Great Britain. While on vacation at her family's beach house in Blankenberge she met Rafael Ángel Calderón Guardia, then a young foreign student. She married the future Costa Rican president in Antwerp on July 28, 1927.