The Kaliningrad K-5 (NATO reporting name AA-1 Alkali), also known as RS-1U or product ShM, was an early Soviet air-to-air missile.

An improved variant, K-5M or RS-2US in PVO service, entered production in 1959, matched to the RP-9/RP-9U (Sapfir) radar of the Sukhoi Su-9.

The People's Republic of China developed a copy under the designation PL-1, for use by their J-6B fighters.

The difficulties associated with beam-riding guidance, particularly in a single-seat fighter aircraft, were substantial, making the 'Alkali' primarily a short-range anti-bomber missile.

The K-55 remained in service until about 1977, probably being retired with the last of the Sukhoi Su-9 interceptors.