Which was the world's first space station?

Salyut 1 was the first space station of any kind, launched into low Earth orbit by the Soviet Union on April 19, 1971. The Salyut program followed this with five more successful launches out of seven more stations. The final module of the program, Zvezda (DOS-8) became the core of the Russian segment of the International Space Station and remains in orbit.

Salyut 1 originated as a modification of the military Almaz space station program then in development. After the landing of Apollo 11 on the Moon in July 1969, the Soviets began shifting the primary emphasis of their manned space program to orbiting space stations, with a possible lunar landing later in the 1970s if the N-1 booster became flight-worthy (it did not). One other motivation for the space station program was a desire to one-up the US Skylab program then in development. The basic structure of Salyut 1 was adapted from the Almaz with a few modifications and would form the basis of all Soviet space stations through Mir.