Musk praised Denholm's input in her time on Tesla's board.
"I believe in this company". Musk's brother, Kimbal, is one of the members.
Denholm, 55, has been an independent director of Tesla since 2014 and the head of its audit committee. "She's not a proven entity in this kind of work", she said. "Do you ask the person who helped get you lost in the woods to help drive you out of the woods?" The firm said her post as board chairwoman will be a full-time position. "You really have got to wonder", he said.
The regulator declined to say on Thursday if it had approved the appointment of Denholm.
Tesla shares were up 1.4 percent in morning trading.
Musk was named chairman in 2004 after becoming the largest investor.
Musk had to step aside as chairman for three years and was also fined, but was able to remain Tesla's CEO.
Executive recruiter Patricia Lenkov, however, said that Denholm likely was not the right pick for the job, arguing Tesla needed a figure with more experience dealing with strong founders.
Prior to working at Telstra, Denholm spent seven years at Toyota in Australia, where she was a senior financial manager.
This announcement counters the rumors reported earlier by The New York Times and The Financial Times that Tesla non-executive director and Murdoch media-empire scion James Murdoch was the lead candidate for the chairman role.
Australia's Robyn Denholm will become the new chair of Tesla's board, replacing Elon Musk.
Despite the scandals, Tesla made a profit of $312m in the third quarter, well ahead of Wall Street forecasts, with revenues of $6.8bn.
Tesla Inc.'s (TSLA) hunt for a new board chair is over.
Musk had to resign as Tesla chairman under a September arrangement with U.S. regulators to settle fraud charges stemming from a tweet in which he said he planned to take the firm private and had financing to do it. The money will go to shareholders who lost money following Musk's tweet.
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