Sergio Arturo Castro Martínez (born 12 March 1941) is a Mexican humanitarian who resides in San Cristóbal de las Casas, Chiapas, Mexico.

However, by nature he is a true humanitarian, ethnologist and polyglot (languages include Spanish, French, Italian, English, Tzotsil, Tzeltal and Mayan fluently).

Castro has spent more than 45 years helping to build schools, develop water treatment systems and provide wound care for burn victims for the many indigenous cultures and Mexican people of Chiapas.

He has helped to build more than 35 schools and numerous water catchment and treatment systems in the San Cristóbal area and surrounding Maya villages.

Museo de Trajes Regionales – Over the years, for his service, Castro has been given tribal garb, statuettes, masks, tools, and decorative items from the villagers he has helped.