Audi has announced it will not take part in the DTM beyond the 2020 season, leaving BMW as the series' only manufacturer.
Having made the announcement on Monday, Audi cited the desire to focus its energies on its Formula E and customer racing projects and also the negative economic consequences of the global coronavirus pandemic.
A stalwart of the DTM since its resurrection in 2000, Audi had been known to be weighing up its future involvement in the German tin-top series even before the COVID-19 crisis.
The decision follows parent brand Volkswagen's decision to terminate its non-electric motorsport programmes last year.
Audi's Rene Rast won his second DTM title in three years last season, taking Audi's tally to nine championships in the post-2000 era - second only to Mercedes, which withdrew after the 2018 season.
It had also won back-to-back titles in the old DTM in 1990 and '91 before moving onto Super Touring.
"Audi has shaped the DTM and the DTM has shaped Audi," commented Markus Duesmann, Audi's Chairman of the Board of Management.
"This demonstrates what power lies in motorsport - technologically and emotionally.
"With this energy, we're going to drive our transformation into a provider of sporty, sustainable electric mobility forward.
"That's why we're also focusing our efforts on the race track and systematically competing for tomorrow's 'Vorsprung.'
"Formula E offers a very attractive platform for this. To complement it, we're investigating other progressive motorsport formats for the future."
Audi is currently set to operate nine cars in the 2020 DTM season, while BMW will operate seven to complete a 16-car field.
The R-Motorsport-operated Aston Martin team withdrew prior to the season, meaning Audi's withdrawal is the second in a matter of months.
Gerhard Berger, the chairman of DTM's promoters ITR, called Audi's announcement "difficult" for the series to take, and called for a more "united approach" following the manufacturer's withdrawal.
"Today is a difficult day for motorsport in Germany and across Europe," Berger said.
"I deeply regret Audi's decision to withdraw from the DTM after the 2020 season.
"While we respect the board's position, the short-term nature of this announcement presents ITR, our partner BMW and our teams with a number of specific challenges.
"Given our common association, and the particular difficulties we all face during the COVID-19 pandemic, we would have hoped for a more united approach.
"This decision worsens the situation, and the future of the DTM now very much depends on how our partners and sponsors react to this decision.
"Nevertheless, I fully expect Audi to undertake its planned exit properly, responsibly and in full partnership with ITR.
"My commitment remains to the year ahead, and to ensuring we provide our hundreds of thousands of fans with a thrilling and competitive season.
"But, as soon as possible, I also want to create planning security for our participating teams, sponsors and everybody whose job depends on the DTM."