Why did King Henry III of France name Henry of Navarre as his successor?

King Henry III of France named Henry of Navarre as his successor because he had no legitimate male heir to inherit the throne, and the Valois dynasty was nearing its end.12

Following the assassination of the duc de Guise and the subsequent open war declared against him by the Holy League, Henry III was forced to seek protection from his cousin, Henry of Navarre. When Henry III was fatally stabbed by a fanatical friar in 1589, he used his final moments to formally commend Henry of Navarre to his courtiers as his rightful heir. He also exhorted him to convert to Catholicism, a step Henry of Navarre eventually took to secure his position as the national sovereign, King Henry IV.12