On 21 May 2024, Russia launched 29 drones at Ukraine and faced significant losses; Ukraine repelled most attacks, inflicted battlefield losses, and continued defense preparations amid ongoing drone and missile strikes.

On 21 May 2024, Russia launched 29 UAV drones against Ukraine, with Ukrainian air defenses successfully shooting down 28 across seven regions. In Kharkiv, drone debris caused injuries to four civilians aged 61-72 and one man was injured by rocket strikes on transport infrastructure. Ukrainian forces report nearly 1400 Russian combatant casualties and significant vehicle losses near the frontline. Russia suffered a drone strike on a fuel depot in Shebekino, Belgorod region, with no reported injuries. Ukrainian intelligence observed Russian military personnel moving disguised as civilians, with an estimated 600 moving from Tula to Luhansk. Ukraine confirmed destroying the Russian missile carrier Cyclone in Sevastopol harbor. Meanwhile, Russia continued drone attacks on Ukrainian energy infrastructure in Sumy region, hitting substations in Shostka and Konotop with four explosions reported. Poland arrested nine individuals accused of sabotage ordered by Russian special services. Germany's Foreign Minister visited Kyiv reaffirming solidarity and Romania prepared new military aid. Ukrainian forces have completed training a group of ten personnel to maintain F-16 aircraft, aiming to recruit 4-5,000 individuals. Reports also indicate Russian illegal appropriation of apartments in occupied Ukraine and losses of Russian boats due to spring ice drifts in Yakutia. Despite ongoing fighting and drone attacks, Ukrainian forces state the situation in Kharkiv region remains under control with strengthened defenses after recent assaults.