Ferrer - aiming to qualify for the ATP World Tour Finals in London - on Friday rallied from a set down to topple Dutchman Igor Sijsling, but had no answer when Benneteau assumed control in the last-four encounter. The Frenchman won 6-4 6-1 in one hour 38 minutes.
Benneteau broke the world number five's serve three times in a topsy-turvy first set in which he also lost his own serve twice. He then made the most of the two break points he established in the second set, and held firm to save all nine earned by Ferrer.
The world number 37 will face Juan Monaco in Sunday's final after the Argentinian second seed ousted Japan's Kei Nishikori 6-2 2-6 7-6 (7/4) in two hours 43 minutes to advance to his fifth ATP Tour final of the year.
Third seed Nishikori responded well after Monaco breezed through the first set and comfortably took the second to force a decider.
Monaco, ranked joint 12th in the world, saved a match point at 2-5, though, and then made Nishikori rue his missed chance by battling back to win on a tie-break.