According to Russia's Defence Ministry, Chief of the General Staff Valery Gerasimov will take over as top commander.
The move makes Gerasimov directly accountable for what Russia calls its "special military operation" in Ukraine. It's a demotion for General Sergei Surovikin, who is nicknamed "General Armageddon" by the Russian media for his reputed ruthlessness. He was in the job for just a few months.
In a statement by the Defence Ministry, they said the reshuffle was meant to improve contacts between different military branches and the "quality and effectiveness" of the command structure.
It all comes as Russian and Ukrainian forces engage in intense fighting over the eastern Ukrainian mining town of Soledar.
Russia's private military firm Wagner said they had captured the town.
But in a video address released moments earlier, Ukrainian President Volodymyr Zelenskiy denounced any claims that Soledar had been taken.
"Now the terrorist state and its propagandists are trying to pretend that some part of our city of Soledar - almost completely destroyed by the occupiers - is some kind of Russian achievement."
Zelenskiy said the "fighting continues," and that they will strengthen Ukraine's defences.
Footage released by the State Border Guard Service of Ukraine purportedly showed Russian troops under fire in Soledar.
Reuters was able to confirm the location but was not able to independently confirm the date the clips were filmed.
