ABC staff have downed tools for the first time in 20 years, fighting for an improved pay offer and better working conditions at the national broadcaster.
A 24-hour strike began at 11am AEDT on Wednesday as staff protest the widespread use of short-term contracts and limited career progression, along with a pay deal offering a below-inflation increase.
ABC's main news channel will lean heavily on BBC World News throughout Wednesday while a re-run of Australian Story will replace the 7pm news bulletin on the broadcaster's main channel.
Flagship current-affairs program 7.30 will be replaced by a Hard Quiz re-run.
Moments before the strike began, in a shot showing mostly empty desks, ABC24 host Gemma Veness reminds viewers about the strike and its impact.
'The ABC is planning to continue delivering some services and emergency broadcasting will not be affected by the strike,' she said.
ABC News Breakfast host James Glenday confirmed on air that his show would not be broadcast on Thursday due to the strike.
Some other radio programming is set to be replaced by BBC content.
On-air presenters, including those set to strike, had begun using their platform to inform viewers about the industrial action on Tuesday.
'(Wednesday's) programming will look a little bit different ... my colleagues and I are going to be on strike,' ABC Canberra radio host Alice Matthews said on air.
'We're asking ABC management to make sure our pay grows, at the very least, in line with (inflation), among a few other things related to job security and AI.'
Large gatherings were expected outside ABC offices nationwide, including in Melbourne and Sydney, during the 24-hour strike.
The Community and Public Sector Union and the Media, Entertainment and Arts Alliance are representing staff taking action.
'We've been in bargaining for a long time now with the ABC and what we want to see is a pay off that reflects cost-of-living pressures and actually respects the really important work that the ABC do,' CPSU national secretary Melissa Donnelly told AAP.
'ABC plays such an important role in our society and in Australian storytelling and it's really important ABC management come to the table.'
About 60 per cent of ABC staff rejected management's offer that included a 10-per-cent pay rise across three years.
The unions are also demanding greater night-shift penalty rates, reproductive health leave and rules relating to artificial intelligence.
'Experienced journalists and media workers are being asked to do more with less - with fewer opportunities for pay progression, less certainty about their future, and growing workloads,' MEAA chief executive Erin Madeley said.
It will be the broadcaster's first major strike since 2006.
ABC managing director Hugh Marks said the offered pay deal was financially responsible and competitive for the industry.
'The average tenure of an ABC staff member is more than 10 years, which is three times the economy average ... over 90 per cent of ABC staff are ongoing employees,' Mr Marks said.
'The pay offer reflects the maximum level the ABC can sustainably provide and is balanced when looking across all the factors that we need to consider.'
More than 4,400 people work at the ABC, including 2,000 in news, the largest division.