Oscar Emilio León Simoza, better known as Oscar D'León (b. July 11, 1943) is a Venezuelan musician who became internationally famous for his salsa music. In Spanish, he is known as El Sonero del Mundo ("the Improviser of the World"). His most famous song is perhaps "Llorarás," which he recorded in 1975 with his group La Dimensión Latina.

D'León was born in Caracas on July 11, 1943. A long-time resident of the Parroquia Antímano section of the city, he took interest in bass guitar early on, and would alternate in jobs as an auto mechanic (during the day) and bass player (at night) for local conjuntos. As he acquired a reputation for being a solid bass player, clever improviser (he would improvise entire songs on the spot) and dynamic singer (he used to dance with a double bass onstage while singing, a not-so-subtle physical feat), he founded orchestras such as La Golden Star and music groups such as Los Psicodélicos. Together with percussionist José Rodríguez and trombone players César Monge and José Antonio Rojas, he formed La Dimensión Latina in 1972.

Four years later, D'León quit the group and created La Salsa Mayor. With La Salsa Mayor he recorded merengue standard "Juanita Morell" as a guaracha, a version that became a huge radio hit in Puerto Rico. He later founded La Crítica in 1978 in memory of the legends of Cuban rumba, such as Miguelito Valdés. For a while, D'León would alternate singing with both orchestras, giving him enough flexibility to stay working constantly.

During the 1980s, D'León achieved success in salsa music, and is now one of the great singers of Caribbean music. Meanwhile, he got tired of carrying around his double bass, "and opening the case at baggage claim on the airport only to find it reduced down to toothpicks"; therefore, he gave up playing a bass guitar on stage. He also started shaving his head regularly, as to not bother with alopecia any longer.

Because of successful tours throughout America and Spain, D'León was the first latino to sign a contract with the BBC.