Nils Gustaf Ekholm (9 October 1848 – 5 April 1923) was a Swedish meteorologist who led a Swedish geophysical expedition to Spitsbergen in 1882–1883.
Ekholm was born in Smedjebacken in Dalarna, son of a pharmacist. Having completed his mogenhetsexamen in 1868, he enrolled at the University of Uppsala in September 1869, and graduated with a Candidate of Philosophy degree in 1876, completing a Licentiate degree in 1887 and a Ph.D. in 1888. He was a student of Robert Rubenson and Hugo Hildebrand Hildebrandsson.
He worked at the Meteorological department in Uppsala from 1876 until 1881, and again, after returning from his Spitsbergen expedition, 1884–1890, and was docent of meteorology at the university 1888–1892. From 1890 he worked as an assistant at the Swedish Meteorological Institute in Stockholm (one of the predecessor institutions of the current Swedish Meteorological and Hydrological Institute, SMHI, now located in Norrköping). He became professor and head of the institute in 1913, retiring at the age of 70 in 1918.
Originally responsible only for the meteorological research of the 1881-83 Spitsbergen expedition, Ekholm was made head of the expedition as a whole after his predecessor, Commander F. Malmberg, had become unable to participate because of illness. One of the members of the expedition was the Swedish engineer and balloonist S. A. Andrée, whose North Pole expedition by hydrogen balloon Ekholm was later an original member of. The projected 1896 launch of Andrée's balloon from Spitsbergen was called off because of contrary winds. Ekholm later started to question that the tightness of the balloon was going to be sufficient to keep hydrogen leakage to the minimum necessary for the success of the expedition. When Andrée disregarded his warnings, Ekholm abandoned the expedition. In the 1897 balloon launch, in which the entire expedition perished, Ekholm was replaced by Knut Frænkel.