Sergey Aleksandrovich Ustiugov (Russian: Сергей Александрович Устюгов; born 8 April 1992) is a Russian cross-country skier, world champion and Tour de Ski winner.
Sergey Ustiugov started doing cross-country skiing in the biathlon section of the sports school of the settlement Mezhdurechensky in 2001. His main coach was Ivan Gennadievich Vragin.
In 2011, Ustiugov won gold in sprint at the World Youth Cross-Country Skiing Championships in Otepää, Estonia. A year later he became four-times champion of the Youth Championships in Erzurum, Turkey, in the events sprint, 10 km race, skiatlon and relay as part of the Russian team. In 2013, he participated at the Junior Championships in Liberec, Czech Republic in the Under-23 classification, winning there two gold medals in 15 km free style and 30 km skiatlon. At the Junior Championships in Val di Fiemme in 2014 he won gold in individual sprint.