However, Telstra said in a financial filing of its own [pdf] that while the Tesla role would begin on November 13, Denholm would have to continue in the CFO and head of strategy role at the telco until May 6, 2019.
Electric auto company Tesla has appointed an executive at Australian company Telstra to chair its board.
Mr Musk agreed to step down as chair last month to resolve claims of fraud brought by USA financial regulators.
The move scotches reports that James Murdoch might have been appointed to the job.
The announcement comes after Musk was ousted as board chair in September as part of a settlement with the SEC, which filed a lawsuit against him following an August tweet in which he said he was considering taking the company private, surprising investors, analysts and the board.
That alluded to shortsellers, investors who have bet that Tesla shares will fall and who are frequently the subject of Musk´s derision.
Under that settlement he and Tesla each had to pay a $20 million fine but Musk was allowed to stay on as CEO.
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In a resignation letter , Mr Sessions said he "worked to implement the law enforcement agenda" that Mr Trump campaigned on. Bush administration as U.S. attorney for Iowa's Southern District from 2004 to 2009.
Tesla has seen months of turbulence since Musk's infamous tweet.
"We are undertaking a search for a new chief financial officer and will provide an update on a replacement appointment as soon as possible", Mr Penn said.
"I look forward to helping Elon and the Tesla team achieve sustainable profitability and drive long-term shareholder value", she said in the statement.
She will also be leaving her role as CFO and Head of Strategy at Telstra, Australia's largest telecommunications company, after a six-month notice period there, to focus on her work as Tesla chair full-time, the company said in a statement.
Musk will help ease the new board director´s transition, Tesla said.
Besides Telstra, Denholm has worked in other tech companies such as Juniper Networks and Sun Microsystems, and she also worked for Toyota, the statement added.