Baltacha defied a rankings difference of over 50 places to win the second-round match 6-2, 7-5 in one hour and 34 minutes. The 26-year-old Scot's gutsy win means she will play in the third round of a grand slam for just the third time in her career after advancing to the last 32 at Melbourne Park in 2005 and at Wimbledon in 2002.
It was also just the fourth win of her career against a top-50 rival and after reaching a career-high ranking of 83 earlier this month – which earned her direct entry to a grand slam for the first time – her victory was earned on the back of 35 winners.
Baltacha started confidently as she broke Bondarenko's opening two service games to jump 3-0 ahead in the first set. Bondarenko fought back to 3-2, but with her serve misfiring Baltacha was again able to string a run of three games together to win the first set in 35 minutes.
Bondarenko did not win a single point on her second serve in the first set as the Briton's aggression, paid dividends. The second set was a see-sawing battle with Bondarenko racing 3-0 ahead on the back of some more consistent serving. But again Baltacha, who beat Bondarenko's sister Alona to reach the second round at Wimbledon last year, was again able to put a run of games together.
The Briton won the next four, fending off three break points along the way, to steal the initiative and leave Bondarenko covering her face with her towel at the change of ends. And while Bondarenko broke again Baltacha got her chance to serve for the match at 6-5 and did not waste the chance with the 23-year-old Ukrainian conceding the match when she hit a forehand long.
Baltacha claimed her improved form was down to her growing belief after breaking into the top 100 for the first time at the end of last year. "It's confidence. I used to look back. I used to do that a lot. I'm fed up doing that," she said. "It's all about looking forwards. I just kept thinking, 'You are good enough'."
Baltacha now faces No2 seed Dinara Safina, who reached the final at Melbourne Park last year, in the third round.
Safina beat Barbora Zahlavova Strycova of the Czech Republic 6-3, 6-4. "Safina is a good player. She has had an injury recently and I'll have nothing to lose," said Baltacha. "I'll have a day off and recharge."
Meanwhile, Justine Henin proved she is a genuine contender for this year's title after she beat fifth seed Elena Dementieva in straight sets. The seven-time major winner has been touted as a possible winner after returning from 20 months on the sidelines to reach the final in Brisbane a fortnight ago, and strengthened her claims after winning 7-5, 7-6 (8-6) in the second-round match. Henin's fellow recently returned Belgian, Kim Clijsters, also booked her passage to the third round along with top seeds Svetlana Kuznetsova, Caroline Wozniacki and Jelena Jankovic.
But for Henin it was an emotional night. "It was a great match. It was very emotional for me on the court at the end because there was so much intensity," she said.
"To play this kind of match in the second round, for me, after two years off in a grand slam, it's just the kind of situation that I needed."
Clijsters prevailed in a tough second-round match with veteran Tamarine Tanasugarn, winning 6-3, 6-3. The 26-year-old Belgian, however, was far from comfortable against the heavy hitting of her 32-year-old Thai opponent and needed one hour and 39 minutes to fend off the challenge from the world No99.
"Tammy was very tricky," said Clijsters, who will now face 19th seed Nadia Petrova of Russia, a 6-4, 6-4 winner over Estonia's Kaia Kanepi. "
It is very hard to read her game."
Kuznetsova beat fellow Russian Anastasia Pavlyuchenkova 6-2, 6-2 and
now faces Angelique Kerber of Germany, a 6-2, 6-3 victor over 26th seed Aravane Rezai of France. Eighth seed Jankovic beat Britain's Katie O'Brien 6-2, 6-2 and will now meet Alona Bondarenko in the third round.
Other second-round winners were 11th seed Marion Bartoli of France, 27th seed Alisa Kleybanova of Russia, Belgium's Yanina Wickmayer, Russia's Maria Kirilenko, Italy's Sara Errani and Zheng Jie of China.