"Currently, Ukraine needs greater focus on developing the country's defense and security forces, and on diplomatic negotiations," Zelenskyy writes on X.
"Kyrylo has particular experience in these areas and sufficient strength to deliver results," he continues.
The announcement comes at a key stage in the nearly four-year-long war with Russia. Zelenskyy stated on New Year's Eve, after a meeting with US President Donald Trump, that the two were "90 percent" in agreement on a 20-point peace plan.
The 39-year-old Budanov replaces the former chief of staff Andriy Yermak, who was forced to resign in November after a major corruption scandal.
