The Mexican National Welterweight Championship (Campeonato Nacional Peso Welter in Spanish) is a Mexican professional wrestling championship created and sanctioned by Comisión de Box y Lucha Libre Mexico D.F. (the Mexico City Boxing and Wrestling Commission). While the commission sanctions the title, it does not promote the events at which the title is defended. Consejo Mundial de Lucha Libre (CMLL) promotes the events and has the every day control of the championship. The official definition of the welterweight weight class in Mexico is between 77 kg and 87 kg, but is not always strictly enforced. Because Lucha Libre emphasizes the lower weight classes, this division is considered more important than the normally more prestigious heavyweight division of a promotion. Being a professional wrestling championship, it is not won legitimately; it is instead won via a scripted ending to a match or awarded to a wrestler because of a storyline.
The Championship was created in 1934, making it one of the oldest titles still promoted and older than any title promoted in the United States, Canada or Japan. Documentation is unclear on the details of the tournament other than that Mario Nuñez won the title by defeating Tony Canales in the final on June 17, 1934. In the early days of the championship no single professional wrestling promotion had exclusive control of the championship, but as Empressa Mexicana de Lucha Libre (EMLL; later renamed Consejo Mundial de Lucha Libre) became dominant it became the main promoter of the championship, with the Commission pre-approving the champions. After El Felino vacated the title in 1992, control of the championship was granted to Asistencia Asesoría y Administración (AAA), which promoted the title for the next six years. In 1998 control of the Welterweight Championship was returned to CMLL when Arkangel de la Muerte defeated El Toreo on a CMLL show. Since then the title has been promoted exclusively by CMLL.
Karloff Lagarde holds all "longevity" records for the championship. He has had the longest individual reign (1,859 days), the longest combined reign (2,731 days) and the most reigns of any champion, with four. Psicosis holds the record for the shortest reign, having held the title for only two days.