Sin Piedad (2011) was an annual professional wrestling major event produced by Consejo Mundial de Lucha Libre (CMLL), which took place on December 16, 2011, in Arena México, Mexico City, Mexico and replaced CMLL's regular Friday night show Super Viernes. The 2011 Sin Piedad was the tenth event under that name that CMLL promoted as their last major show of the year, always held in December. The main event of the show centered around a long running storyline between Blue Panther and the Casas wrestling family, represented by El Felino in this instance. The two wrestled in a Lucha de Apuesta, hair vs. hair match where the loser of the match would be forced to have all his hair shaved off. The show featured four two out of three falls six-man tag team match and one tag team match with representatives from CMLL's Mini-Estrella division.

Genaro Vázquez Nevarez is a Mexican professional wrestler and trainer, best known under his ring name Blue Panther. He made his in-ring debut in 1978. Since then, he has worked for most major Mexican professional wrestling promotions, including the Universal Wrestling Association (UWA), Consejo Mundial de Lucha Libre (CMLL) and Asistencia, Asesoría y Administración (AAA). He was one of the first wrestlers to leave CMLL for AAA when it was created in 1992, but returned to CMLL in 1997 where he has competed ever since.