The fifth-seeded Sharapova, who won the first of her three Grand Slam titles at the All England Club in 2004, overcame 13 double-faults to beat Sabine Lisicki 6-4, 6-3.
Kvitova reached her first major final by hitting nine aces in a 6-1, 3-6, 6-2 win over Victoria Azarenka.
Sharapova had two double-faults in her opening service game, the second to get broken. She had two more while trailing 3-0, but saved a break point and then won 12 of the final 16 games.
"She played really well and I did quite the opposite," Sharapova said. "It was tough. I just had to stay focused.
I got back on track and just remained really focused throughout the rest of the match." The turning point in the match may have come on that first saved break point.
With Lisicki playing near flawless tennis through the first three games, she turned to the drop shot, which was so effective against Marion Bartoli in the quarterfinals.
But this one went into the net, putting the score at deuce and giving the momentum to Sharapova.
Even though Sharapova's first serve didn't get much better, her game once the ball was in play did, sending forehands and backhands into the corners and passing her outmatched opponent.
Lisicki also got frustrated early in the second set as a light drizzle started to rain down on Centre Court.
Trailing 0-30 and hoping to get a short reprieve, Lisicki asked chair umpire Louise Engzell to suspend play, but was denied.
Three points later, it was 3-0 to Sharapova and Lisicki's chances of reaching a first Grand Slam final were fading fast.
Sharapova, who has not lost a set at this year's tournament, had 18 unforced errors and only 14 winners.
Lisicki did exactly the opposite, with 18 winners and 14 unforced errors.
In the first match, Kvitova rode her big serve right into the final, hitting three aces in a row in the final game of the first set.
"All match it was around both serves, so I'm very happy my serve was good in the third set," said Kvitova, who had never won a match on grass before last year's tournament, when she reached the semifinals. "Grass is my favorite surface." Kvitova was playing in only her second major semifinal, and she dictated the play throughout the match.
The Czech left-hander had 40 winners and 14 unforced errors, while Azarenka had only nine winners and seven unforced errors.
And it was Azarenka's serve that finished it when the fourth-seeded Belarusian committed her second double-fault of the day on match point.
In the first set, Kvitova twice broke Azarenka's serve and saved the only break point she faced. She finished the set with six aces.
But Azarenka responded in the second, finally converting a break point in the second game to take a 2-0 lead. She held the rest of the way and evened the match, but couldn't do much about her opponent's serve.
Kvitova lost only one point in the opening game of the third set, and then broke for a 2-0 lead. At 3-1, Azarenka had two break points, but Kvitova saved them both and then won the next two points to make it 4-1.
Kvitova is the first left-handed woman to reach the Wimbledon final since Martina Navratilova in 1994.
Navratilova, who won the title nine times and was in the crowd Thursday, and Ann Jones (in 1969) are the only left-handers to win the championship dish at the All England Club.
"We met in the locker room and she's told me well done and good luck for the next match," Kvitova said of Navratilova. "It's very nice when I can meet her and speak with her." The last lefty to even reach a women's major final was Monica Seles at the 1998 French Open.