What was the first spacecraft to orbit Venus?

Venera 9 was the first spacecraft to orbit Venus. The Soviet orbiter entered Venusian orbit on 20 October 1975, becoming the first artificial satellite of the planet.

Venera 9 was an orbiter-and-lander mission launched on 8 June 1975. The orbiter studied Venus’s clouds, atmosphere, ionosphere, magnetic environment, and surface using radar-related measurements. It also served as a communications relay for the lander, which descended through the dense atmosphere two days later.

The lander created another landmark: it returned the first photographs taken from the surface of another planet. Its black-and-white images showed a rocky, shadowless landscape beneath the clouds. The lander operated for about 53 minutes before the extreme heat and pressure ended communications.

Mariner 2, one of the listed alternatives, was the first successful spacecraft to fly past Venus, not orbit it. Pioneer Venus 1 became the first American spacecraft to orbit Venus in 1978. Venera 4 was an atmospheric probe and did not achieve orbit, making Venera 9 the canonical answer to this question.