Elections to the National Baseball Hall of Fame for 2019 proceeded according to rules most recently amended in 2016. As in the past, the Baseball Writers' Association of America (BBWAA) voted by mail to select from a ballot of recently retired players. The results were announced on January 22, 2019, with the BBWAA electing Mariano Rivera, Roy Halladay, Edgar Martínez, and Mike Mussina to the Hall of Fame. Rivera and Halladay were elected in their first year of eligibility, while Martínez was elected in his last year of eligibility. Rivera became the first player to be unanimously elected, appearing on all 425 ballots; he broke Ken Griffey Jr.'s record of 99.32 percent, set in 2016.

Mariano Rivera is a Panamanian-American former professional baseball pitcher who played 19 seasons in Major League Baseball (MLB) for the New York Yankees, from 1995 to 2013. Nicknamed "Mo" and "Sandman", he spent most of his career as a relief pitcher and served as the Yankees' closer for 17 seasons. A thirteen-time All-Star and five-time World Series champion, he is MLB's career leader in saves (652) and games finished (952). Rivera won five American League (AL) Rolaids Relief Man Awards and three Delivery Man of the Year Awards, and he finished in the top three in voting for the AL Cy Young Award four times. He was inducted into the Baseball Hall of Fame as part of its class of 2019 in his first year of eligibility, and is to date the only player ever to be elected unanimously by the Baseball Writers' Association of America (BBWAA).