Which Apollo mission had the longest total mission duration?

Which Apollo mission had the longest total mission duration? Apollo 17 had the longest total mission duration.

The final lunar expedition lasted 12 days, 13 hours, 51 minutes, and 59 seconds, from its launch on December 7, 1972, until splashdown on December 19. Its extended schedule reflected the ambitious J-type mission plan: extensive lunar surface exploration, scientific instruments, and a long stay in lunar orbit.

Apollo 17 also set several related records. Astronauts Eugene Cernan and Harrison Schmitt spent about 75 hours on the Moon, conducted three surface excursions, and traveled with the Lunar Roving Vehicle. Command-module pilot Ronald Evans remained in lunar orbit, operating the spacecraft and conducting a deep-space spacewalk on the return journey.

A common mix-up is Apollo 15, which lasted nearly as long at about 12 days, 7 hours. Apollo 17 exceeded it by roughly six hours. “Longest total duration” means the complete mission, not the longest time on the lunar surface or the longest single moonwalk.