The Panteón Nacional Román Baldorioty de Castro is a tract of land in Barrio Segundo of the city of Ponce, Puerto Rico, originally designed as the city's cemetery, but later converted into what has come to be a famous burial place. Established in 1842, it is Puerto Rico's first national pantheon. It is the only cemetery dedicated as a museum in Puerto Rico and the Caribbean. Prior to being dedicated as a Panteón Nacional, it was known as Cementerio Viejo or as Cementerio Antiguo de Ponce, and is listed under that name on the U.S. National Register of Historic Places. The Pantheon is named after Román Baldorioty de Castro, a prolific Puerto Rican politician, and firm believer of Puerto Rican autonomy and independence. His remains are located here. The Pantheon also houses a small museum about the history of autonomism in the Island, and it is currently used both as a park and a venue for the expression of culture and the arts. It is called the Museo del Autonomismo Puertorriqueño.

Segundo is one of the 31 barrios of the municipality of Ponce, Puerto Rico. Along with Primero, Tercero, Cuarto, Quinto, and Sexto, Segundo is one of the municipality's six core urban barrios. It was organized in 1878. Barrio Segundo has 3 subbarrios: Baldority de Castro, Clausells, and Reparada.