Which spacecraft made the first successful flyby of Mars in 1965?

The spacecraft that made the first successful flyby of Mars in 1965 was Mariner 4.

NASA’s Mariner 4 passed Mars on July 14, 1965, after launching on November 28, 1964. It returned the first close-up photographs of another planet, transmitting 21 images that revealed a cratered, Moon-like surface. Those pictures transformed scientific expectations about Mars, which had sometimes been imagined as a world of canals or widespread vegetation.

Mariner 4 did not land or enter orbit; it was a flyby spacecraft. Mariner 2 was a Venus mission, while Viking 1 was a much later Mars lander. Mars 3 reached Mars in 1971 and achieved a partial landing mission, but it did not make the first successful Mars flyby.