Soyuz 11 (Russian: Союз 11, Union 11) was the only manned mission to board the world's first space station, Salyut 1 (Soyuz 10 had soft-docked but had not been able to enter due to latching problems). The mission arrived at the space station on 7 June 1971 and departed on 30 June. The mission ended in disaster when the crew capsule depressurised during preparations for reentry, killing the three-man crew. The Soyuz 11 crew members were Georgy Dobrovolsky, Vladislav Volkov, and Viktor Patsayev.

The three crew members of Soyuz 11 are the only humans to have died in space.

The original prime crew for Soyuz 11 consisted of Alexei Leonov, Valeri Kubasov and Pyotr Kolodin. A medical X-ray examination four days before launch suggested that Kubasov might have tuberculosis, and according to the mission rules, the prime crew was replaced with the backup crew. For Dobrovolski and Patsayev, this was to be their first space mission. After the failure of Salyut 2 to orbit, Kubasov and Leonov were reassigned to Soyuz 19 for the Apollo-Soyuz Test Project in 1975.

...
Wikipedia