Venus rotates extraordinarily slowly on its axis, completing one full spin (its sidereal day) in about 243 Earth days. This figure is confirmed by NASA, the Canadian Space Agency, CNES, and ESO, all of which cite radar measurements first taken in 1962 that penetrated Venus's thick cloud cover to reveal its rotation period.
Adding complexity, Venus rotates in the opposite direction to most planets — a phenomenon called retrograde rotation. This backward spin, combined with its orbital motion, produces a solar day (the time from one sunrise to the next) of only about 116.75 Earth days — less than half the sidereal day. So the answer depends on which definition of "day" you use.
For context, Venus completes a full orbit around the Sun in just ~224.7 Earth days. This means Venus's sidereal day is actually longer than its entire year — a counterintuitive fact highlighted by NASA and the Royal Belgian Institute for Space Aeronomy, which quantifies a Venus year as roughly 0.924 of its sidereal day.