(7 October 1859 - 10 February 1927) was a Norwegian painter. He was best known for interiors and domestic and rural scenes. His artistic style was associated with Naturalism and noted for accurate observations and attention to detail.
Gustav Wentzel was born in Christiania. He was a pupil of painter Knud Bergslien (1879-81) of and Frits Thaulow in 1883. He also studied for a time in Paris at the Academie Julian in 1884 and at Academie Colarossi with Leon Bonnat and Alfred Philippe Roll (1888-89). Wentzel first public painting was exhibited in Albert Cammermeyer bookstore during the autumn of 1879. His painting Snekkersvennen, which had been rejected by the Christiania Kunstforening, led to a lasting dispute and the establishment of an exhibition organized by the artists themselves, which eventually became an annual event called Autumn Exhibition (Høstutstillingen) in Oslo.
Among his paintings at the National Gallery of Norway are I fiskernaustet from 1881, Frokost from 1882, and Dans i Setesdal from 1887. Wentzel was decorated Knight, First Class of the Royal Norwegian Order of St. Olav in 1908