A graph is said to be symmetric if its automorphism group acts transitively on its arcs. In this paper, all connected pentavalent symmetric graphs of order are classified, where are distinct primes. It follows from the classification that there are two connected pentavalent symmetric graphs of order , and that for odd primes and , there is an infinite family of connected pentavalent symmetric graphs of order with solvable automorphism groups and there are seven sporadic ones with nonsolvable automorphism groups.