Klaudzi Duzh-Dusheuski (Belarusian: Клаўдзі Дуж-Душэўскі, Lithuanian: Klaudijus Dušauskas-Duž; 27 March or 26 April 1891, Vileyka – 25 February 1959, Vilnius or Kaunas) was a Belarusian architect, diplomat and journalist. He is believed to be the creator of the Flag of Belarus in 1917.
Dusheuski was born into an impoverished szlachta family. In 1912 he graduated the Vilna non-classical secondary school where he had joined the Belarusian national movement. In 1912–1918 Duzh-Dusheuski has studied in the Saint Petersburg Mining Institute. Being in St. Petersburg, he also took part in Belarusian social life. For instance, he was editor of the Belarusian magazine Ranica.
In 1917 he joined the Belarusian Socialist Assembly. In 1918 he worked at the Refugee Assistance Department of the Belarusian National Committee in St. Petersburg. At that time, according to his own memories, he has created the draft of the white-red-white Flag of Belarus that was very quickly adopted by the Belarusian national movement throughout the European part of the former Russian Empire and later adopted as the state flag of the Belarusian Democratic Republic.
In 1919 Dusheuski moved to Vilna. In autumn 1919 he was appointed diplomatic representative of the Belarusian Democratic Republic in the Baltic states. In early 1921 Duzh-Dusheuski was arrested by Polish authorities.
After that he emigrated to the Republic of Lithuania and settled in Kaunas. In the 1920s–1930s he worked for several ministries there. In 1927 he graduated from the University of Lithuania in Kaunas. Duzh-Dusheuski also edited several Belarusian newspapers in the Republic of Lithuania.
In 1940 Duzh-Dusheuski was arrested by the Soviets who had occupied the Republic of Lithuania. In August 1943 he was arrested by the Nazis for hiding Jews. He was put into the Pravieniskes death camp.
In 1944–1946 Klaudzi Duzh-Dusheuski worked at the Kaunas University.
In 1952 Duzh-Dusheuski was arrested and sentenced to 25 years of concentration camps for being an "active Belarusian nationalist". He was freed in 1955 and has worked for an architectural institute.