Masterstroke finished third and Haya Landa was fourth in a race run over heavy turf.
The race appeared to be over when Orfevre easily ran by the leaders, including Solemia, inside the final furlong and opened up a big and easy lead. But jockey Olivier Peslier never gave up on Solemia and as Orfevre shortened stride in the final 100 yards, the 4-year-old filly flashed by and won by about a neck.
The 1 1/2 miles went in 2:37.68, some 13 seconds slower than last year's time.
The other well-backed runners, including Camelot, St Nicholas Abbey, Shareta and Sea Moon, never figured in the running of Europe's most prestigious race. Last year's winner, Danedream, was caught in a quarantine in Germany and not able to defend her title.
Solemia came into the Arc off a third-place finish in the Prix Vermille, a race won by Shareta. She now has five wins, three second and two thirds from 13 career starts for owner/breeders Wertheimer & Frere.