Oscar Marcelo Alemán (February 20, 1909 – October 14, 1980) was an Argentine jazz guitarist, singer, and dancer. He is widely recognized in his country and abroad as one of the best jazz performers, and as an influential artist.

At the age of six, Alemán joined the family ensemble, the Moreira Sextet, and played the cavaquinho, a Brazilian ukulele, before taking up the guitar. The group travelled to Buenos Aires to perform at the Parque Japonés, Nuevo Theater, and at the Luna Park. Later they toured in Brazil.

Alemán was orphaned at age of ten when his mother died and his father committed suicide. He sustained himself by working sporadically as a dancer and musician on the streets of Santos, Brazil. When he saved enough money, he bought a guitar and started to play professionally at party venues in a duo called Los Lobos with his friend, Brazilian guitarist Gastón Bueno Lobo. The duo moved to Buenos Aires in 1925 to work under contract for the comedian Pablo Palitos. In Buenos Aires, they formed a trio with violinist Elvino Vardaro. They added tango to their repertoire and recorded with Agustín Magaldi. They later played with Carlos Gardel and Enrique Santos Discépolo.