The third-seeded Klizan will face fourth-seeded Fabio Fognini of Italy, who defeated Daniel Gimeno-Traver of Spain 6-3, 6-4 in the other semifinal. Fognini will be playing in his second career final after winning his first title in Romania in April.
Youzhny overcame a 5-3 deficit in the first set and saved three set points in the tiebreaker to win it. Klizan then came back from 4-2 down in the second by winning four consecutive games to force a third set.
He broke Youzhny in the sixth game of the decider and led 5-2 but could not score a point in the next three games, setting up a second tiebreaker. Klizan jumped to 6-3 and sealed the victory after 3 hours, 49 minutes with a powerful first-return forehand on his first match point.
"I was fighting from the beginning to the end, that's why I think I won," Klizan said. "Because I had a very big motivation and I really wanted to win. I had some problems with my back but still was fighting for each point."
Both players called for the doctor: Youzhny's toe was treated; Klizan's back was massaged.
Youzhny, the 2004 champion and a two-time runner-up, said he was lucky in the first tiebreaker and Klizan played better in the second one.
Fognini rallied in the first set by winning four consecutive games. In the second set, he made the decisive break in the seventh game. He converted his second match point, advancing to the net and making a short, low forehand.
"My good serve was the key today," Fognini said.