The refinery is involved in complex oil processing, producing gasoline, fuel oil, diesel fuel, and more than 20 other petroleum products, which are supplied to the Russian army, among others.
The damage caused by the drone strike and subsequent fire at the facility is being assessed.
Earlier in the day, Saratov Oblast Governor Roman Busargin confirmed "damage to an industrial site," without specifying which facility was hit.
The head of the Center for Countering Disinformation (CCD) at the National Security and Defense Council, Andriy Kovalenko, also verified the attack, noting that the Saratov refinery is a crucial part of Russia's fuel infrastructure.
"This is not the first attack," he said.
"The Saratov oil refinery is one of Russia’s key fuel infrastructure facilities, with an annual processing capacity of 7 million tons of oil."
On the same day, Russian Telegram channels reported at least 11 explosions in the area of the Engels-2 air base, also in Saratov Oblast. It houses Tu-95MS and Tu-160 aircraft of the 22nd Heavy Bomber Aviation Division, which are regularly involved in carrying out strikes on Ukraine.