The Kasta 2E (NATO: Flat Face E, alternative name Casta 2E) is a modern Russian radar system.

The development of the Kasta 2E surveillance radars was initiated in the former Soviet Union.

Its primary objective is to overcome deficiencies or to satisfy the demand in low-level surveillance.

The Kasta 2E1 (51U6) system uses two antennas and consists of two vehicles: The Kasta 2E2 (39N6E) system uses one antenna and consists of three vehicles: Both radar types can be triggered with either equal or opposed phases.

On 13 February 2024, near the Russian-Ukrainian border, the Defence Intelligence of Ukraine's Special Forces group struck at the Russian Kasta-2E2 radar.