Claës Christian Olrog (25 November 1912 – 29 November 1985) was a Swedish-born ornithologist who worked in Argentina.
In 1939 he visited Tierra del Fuego as part of his PhD research.
In 1946 he travelled into Paraguay and then took up a teaching position at the Miguel Lillo Institute, in San Miguel de Tucumán, Argentina, in 1948.
He published a field guide to the birds of the region in 1959 - Las Aves Argentinas.
He described several new taxa and several species have also been named after him.