Kvitova, ranked No. 2 in the world, posted a 6-4, 6-4 win over Sara Errani in her quarterfinal Wednesday while Sharapova was a 6-2, 6-3 winner over Ekaterina Makarova.
That semifinal will be a rematch of the 2011 Wimbledon title match, which Kvitova won for her first Grand Slam title.
The other semifinal has defending champion and 11th-seeded Kim Clijsters playing third-seeded Victoria Azarenka. Clijsters, who beat world No. 1 Caroline Wozniacki in the quarterfinals, is the only Australian Open semifinalist who can't move up to No. 1 in the rankings.
Kvitova kept her chances of reaching the top ranking alive by overcoming 44 unforced errors -- against 36 winners -- versus Errani. Kvitova dropped serve four times in 10 games but had six breaks -- three in each set -- and took 52 percent of the point when receiving Errani's serve.
Sharapova, seeded fourth, has lost just one set in her first five matches in Melbourne and continued her solid play Wednesday. She lost her serve just once, despite four double faults and 32 unforced errors. Sharapova won two-thirds of the points on serve and 52 percent when receiving.