Hans Thomas "Hassa" Horn (2 October 1873 – 21 April 1968) was a Norwegian road engineer, industrialist, sports official and politician for the Conservative Party.
He was born in Christiania as a son of civil servant Hassa Horn, Sr. (1837–1921) and Alette Gram (1844–1933). In 1905 he married Helga Birch-Reichenwald (1882–1909), a daughter of Peter Birch-Reichenwald. After her death he married anew, in 1910 to Sigrid Steen (1883–1956), a daughter of Johan Steen and sister of Erling Steen. Through his older sister Dorothea, Hassa Horn was an uncle of national housewives' leader Alette Nicolaysen.
He graduated in engineering from Kristiania Technical School in 1893, and studied at the Dresden College of Engineering from 1895 to 1897. He was then hired in the Norwegian Public Roads Administration in Nordland, with transfers to the Norwegian Directorate of Public Roads in 1901 and road planning in the Faroe Islands in 1903. He was hired as chief of the Public Roads Directorate executive office in 1905, and remained so until 1918. He then had a stint as construction chief for Electric Furnace Prod. Co. in Sauda until 1921.
Horn was a Nordic combined skier in his youth, with a specialty in ski jumping. He represented the club SK Skuld. He became chairman of the Association for the Promotion of Skiing from 1908, and remained so until 1912. In 1910 he was a participant in the splintering of Norwegian sports organizations, as the new Norges Riksforbund for Idræt (Confederation of Sports), which favored modern competitive sports, broke away from Centralforeningen which favored military sports and exercise. Horn also chaired the Norwegian Ski Federation (1914–1918) and the Norwegian Lawn Tennis Federation, and from 1908 to 1918 he also served as secretary of the Norwegian Trekking Association from 1908 to 1918, and edited its yearbook. He shared the Holmenkollen medal in 1918 with Jørgen Hansen.