Monfils will meet top-seeded Tomas Berdych, who beat Philipp Kohlschreiber of Germany 6-3, 6-4. Berdych is going for his first title since winning the China Open in October. Monfils is playing in his second final this season following the Qatar Open last month.
Simon, seeded second, rallied from a 3-0 deficit in the final set to 4-4, but dropped serve again to lose.
In the first set, Monfils whipped a forehand winner to break for a 2-1 lead, but Simon broke back in the sixth game with a backhand return winner. Simon put Monfils under pressure at 5-4 and took the first set when Monfils netted a forehand.
Monfils saved eight break points in the second set, including a match point at 6-5, to force a tiebreaker. He evened the match at one set apiece on a forehand error by Simon.
In the later semifinal, Berdych broke Kohlschreiber once in each set and saved all five break points he faced. The Czech clinched victory when Kohlschreiber netted a backhand.