McEwan joins the NAB from the Royal Bank of Scotland (RBS), where he had been the CEO since 2013.
The 62-year-old New Zealander said there were parallels between his work in restoring profitability at RBS and the challenge that lay ahead of him in Australia. He was also CBA's executive general manager.
McEwan announced in April that he was leaving RBS.
Mr Baird, who in 2017 agreed to join NAB in an executive role just six weeks after resigning as NSW premier, was initially rumoured to be among the candidates for the role before the bank opted for an external appointment.More news: JCPenney To Hire Restructuring Firm: Can The Retailer Avoid Bankruptcy?
"Ross brings a compelling range of experience across finance, insurance and investment with a track record of delivering important and practical improvements for customers", said chairman-elect Phil Chronican. "RBS has been through numerous same challenges which NAB now faces around culture, trust and reputation", Chronican says.
"We have secured a well proven CEO and reached agreement on an appropriate remuneration package when compared with domestic and worldwide peers and other sectors".
The appointment means that Mr Chronican will transition from interim CEO to the Chairman position in mid-November 2019, replacing Dr Ken Henry.
NAB had spent five months searching for a new CEO following the resignation of former boss Andrew Thorburn in the wake of the royal commission.
McEwan is also seen as an experienced banker who has dealt with numerous issues now facing the Australian banks, including an increasingly tough revenue environment.More news: Emery confident Arsenal will soon have 'three or four' new players
"Customer service and delivery are what can differentiate us".
"It does take a long time to fix reputations of an institution such as this".
"There's no silver bullet to fix the reputation or improve customer service. It's every interaction with every person every day has to be a great interaction with a customer, with the customer at the centre of that", he said.
McEwan was reported as saying he would accelerate the NAB's transformation in line with community expectations of high accountability and transparency in the banking industry.
The company announced in May it had set aside Aus $1.1 billion in the last financial year to compensate customers.More news: Eagles agree to terms to re-sign RB Sproles
Australia's Royal Commission found NAB charged almost 100 million Australian dollars (£56.4 million) for services that never existed.