President Salva Kiir has relieved Warrap State governor Bona Panek Biar, replacing him with Aleu Ayieny Aleu.
Bona Panek Biar was among eight governors appointed into the government of national unity in June 2020.
The change was announced on the state-run South Sudan Broadcasting Corporation on Thursday evening.
However, the decree did not mention why the governor was dismissed, even before he formed his state government.
In a separate decree, Kiir appointed Yath Awan Yath as the undersecretary of information in the ministry of information communication technology and postal services.