Cidadão Quem was a Brazilian rock band formed in 1990 in the city of Porto Alegre, Rio Grande do Sul. The original line-up of the band included Duca Leindecker (vocals, acoustic guitar and electric guitar), his brother Luciano Leindecker (bass) and Cau Hafner (drums).

Cau died on July 10, 1999, in a parachuting accident, at the age of 39. Luciano, after an 8-year battle with cancer, died on November 21, 2014, at the age of 42.

The band's name was inspired by the film Citizen Kane, by Orson Welles.