The BTR-4 Busefal ('Bucephalus') is the most modern Ukrainian-designed infantry fighting vehicle which follows from the success of the earlier BTR-3. Unlike the BTR-3 which was based on that of the Soviet/Russian BTR-80, the BTR-4 is a new design from the ground up which correct many of the BTR-80s flaws. The most notable of this is the change in layout which sees the engine compartment moved to the center of the vehicle (behind the driver and commander) and the rear of the vehicle composed entirely of the crew compartment. This allows troops to enter and exit the vehicle from two rear doors, rather than the inconveniently located side doors in the BTR-80 which left them exposed when unmounting. Like the BTR-3, the BTR-4 is heavily armed hence its more appropriate designation as an IFV. The BTR-4 is equippd with a new Thunder weapons module which is fitted with a 30-mm ZTM-2 autocannon, a KT-7.62 coaxial gun, four Konkurs or Baryer ATGMs, and an optional 30-mm AG-17 automatic grenade launcher (in place of two of the ATGMs). The Shkval module on the BTR-3 can also be equipped alternatively. The BTR-4's basic armor protects against small arms and shrapnel but it can also be fitted with additional modular armor. There is also NBC protection and is fully amphibious thanks to twin water jets mounted at the rear. The BTR-4 entered service with the Ukrainian army around the time of the initial hostilities with Russian and separatist forces in 2014 and saw action during that conflict as well as later during the Russian invasion of 2022 where its protection has been praised. The BTR-4 received export orders from Indonesia, Iraq, Nigeria, and Myanmar, although some orders were cut back due to quality issues.

The prototype of the BTR-4 was completed in 2006. Aside from the basic IFV version (BTR-4E for export), it has also been configured for a multitude of additional roles including the BRM-4K reconnaissance vehicle, BTR-4K command vehicles, BTR-4KSh staff vehicle, BMM-4 series of medical vehicles, and BREM and BSEM-4K armored recovery vehicle. Up-armored variants are known as the BTR-4MV1 while a fire support version is known as the MOP-4K.