Ryhor Kastusioŭ (Belarusian: Рыгор Андрэевіч Кастусёў; Russian: Григорий Андреевич Костусёв) (17 April 1957 in Tekhtin, Mogilev Region) is a Belarusian politician, head of the Mogilev regional Coalition of Democratic Forces.

After completing his military service (1975-1977) in the Soviet Armed Forces and training at the Belarusian Agricultural Academy (1977-1982) he returned to his state farm as the head of the workshop, and since 1983 he became the chief engineer.

On the night of December 19–20, he and several other candidates (Nikolai Statkevich and Andrei Sannikov) were detained for organizing and participating in protests against electoral fraud.

[2] On April 12, 2021, he was detained by the KGB of Belarus at his home in the city of Shklov, Mogilev Region and placed in a pre-trial detention center in the capital Minsk.

Kastusiou, Alyaksandr Feduta and Yuras Zyankovich were accused of attempting a military coup.

On September 5, 2022, the Minsk District Court sentenced Rygor Kastusiou to 10 years in prison.