Gualterio Looser Schallemberg (September 4, 1898, Santiago – July 22, 1982) was a Chilean botanist and engineer of Swiss parentage.

Despite his desire to study engineering, Looser worked in his father's industry, a factory producing agricultural spare parts in Santiago, along with his sister Elena.

He also created a significant library, comprising volumes on botany, archaeology, and ethnology, which grew rapidly as Looser acquired any books related to science.

Looser discovered 29 species, along with a subgenus of moss, and amassed a herbarium of over 40,000 plant specimens, which, after his death, was donated to the Aellen Foundation in Switzerland.

On February 3, 1943, he was a founding member of the Chilean Folklore Association (currently the Society of Chilean Folklore) alongside individuals like Aureliano Oyarzún Navarro, Ismael Edwards Matte, Domingo Santa Cruz, Oreste Plath, Ricardo Donoso, Raúl Silva Castro, Benedicto Chuaqui, Andrés Sabella, Carlos Lavín, Oscar Cortés, Humberto Grez, Leopoldo Pizarro, Vicente Reyes Covarrubias, Víctor Castro, Gualterio Looser, Luis Gómez Catalán, Alberto Ried, Remigio Acevedo, Carlota Andrée, María Luisa Sepúlveda, Camila Bari de Zañartu, Emilia Garnham, Carlos S. Reed, Sady Zañartu, Juana Risi de Maldini, and María Bichón.

Several authors have commemorated Looser with specific epithets: His collections were deposited in the Conservatory and Botanical Garden of the city of Geneva.