Efrén Tiburcio Márquez (February 22, 1973 – December 23, 2019), known under the ring name Mr. Niebla, was a Mexican luchador enmascarado (Spanish for masked professional wrestler) who worked for Consejo Mundial de Lucha Libre (CMLL). "Niebla" is Spanish for "fog". His in-ring style focused more on comedy, which often included pratfalls (a form of physical comedy based on falling on the buttocks), dancing and mocking his opponents during matches.