Dmytro Dedko (Demetrius Dedko, Ukrainian: Дмитро Дедько) was a Lord of Ruthenia in 1340 (1323) – 1349. Commonly thought to be a Galician boyar, he could be one of sons of Yuriy I and Varvara (Barbara). Dmytro is possibly the progenitor of Ostrozky family.
Dmytro is mentioned in number of scientific works on history of that period such as "History of Ukraine-Ruthenia" by Mykhailo Hrushevsky, "Die polnische Geschichtschreibung des Mittelalters" by Heinrich Ritter von Zeissberg and others. The Russian historian Alexander Presnyakov argues Hrushevsky's claims that Dmytro was representative of Liubart in Galicia, rather in his declarations Dmytro states that Galician princes are his ancestors.[1]
Among the most solid historical benchmarks signed by Dmytro in 1341 is a document "Letter to residents of Torun" that survived to our days where he calls to revive economical and social relationships between the city of Toruń and Halychyna.
During the Polish-Hungarian aggression against the Kingdom of Ruthenia, Dmytro successfully defended governed territory with support of his brother-in-law Liubartas.
With the death of Dmytro and agreement with the Khan of Golden Horde Janibeg, Casimir III occupied Halychyna in 1349. In return for the Halychyna occupation, Poland promised a tribute to Golden Horde.