Soyuz 23 (Russian: Союз 23, Union 23) was a 1976 Soviet manned space flight, the second to the Salyut 5 space station. Cosmonauts Vyacheslav Zudov and Valery Rozhdestvensky arrived at the station, but an equipment malfunction did not allow docking and the mission had to be aborted.

The crew returned to Earth, but landed on partially frozen Lake Tengiz, the first splashdown in the Soviet space program. While there was no concern about any immediate threat to the crew, the capsule sank under the surface of the frozen lake, and recovery took nine hours owing to fog and other adverse conditions. The landing marked the final splashdown of a manned spacecraft to date.

Soyuz 23 was launched 14 October 1976 with an estimated 73- to 85-day mission planned aboard the orbiting Salyut 5 space station. Others suggest a 17- to 24-day mission was a more likely intention. It was the first visit to the station after the sudden termination of the Soyuz 21 mission in August. However, on 15 October, during the automatic approach phase, the automatic docking system malfunctioned before the craft was within 100 metres of the station. Crews were normally trained for a manual dock, but not for a manual approach. The mission, accordingly, had to be abandoned.

The craft had only two days of battery power, so systems were powered off, including the radio, to conserve power. The day's landing opportunity had already passed, so they had to wait for the next day's landing opportunity near the Baikonur Cosmodrome.

On 16 October, Soyuz 23 returned to earth and landed 8:45 p.m. local time, but weather conditions were poor and the cosmonauts experienced an unusual recovery. They landed on a freezing Lake Tengiz, 8 km from shore, in the middle of a blizzard, with fog and temperatures at −22 °C. It was the first water landing by a Soviet crew. The capsule was designed to land in any conditions, even in a body of water, so the only concern was the increased difficulty in finding the capsule and crew.

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