A worker sorts packages on Amazon Prime Day in New York, July 8, 2025.Klaus Galiano | Bloomberg | Getty ImagesAmazon on Thursday announced it's partnering with OpenAI to let its advertisers run ads in ChatGPT, starting with select brands in the U.S. It marks a vote of confidence from the world's largest online retailer in OpenAI's burgeoning ad business, which recently reached a $1 billion annualized revenue run rate. OpenAI started selling sponsored placements in ChatGPT in the U.S. in February, starting with retailers like Best Buy and Williams-Sonoma.Amazon has heavily restricted access to its sprawling webstore from artificial intelligence platforms like ChatGPT, Anthropic's Claude and Google's Gemini, while investing in its own AI shopping tools. But in recent months, Amazon began quietly buying ads on ChatGPT, and it became the top retail company advertising on the platform between April and August, according to data from market intelligence firm Sensor Tower. By letting brands that advertise on Amazon run ads in ChatGPT, the Andy Jassy-led giant is acknowledging that the platform has become an important marketing channel. OpenAI said in February that ChatGPT reached 900 million weekly active users. Amazon said in a blog post that conversational ad formats like those that appear in AI chatbots are the "fastest growing engagement opportunity" for brands to reach new and existing customers. "With Access to ChatGPT Ads, advertisers can now extend their campaigns further into where their customers are actively spending time in conversational chat platforms," Chris Conetta, director of omnichannel supply at Amazon's demand-side advertising platform, said in a statement. Ad campaigns are set up and managed by Amazon, while OpenAI's ads system controls all ad delivery decisions, an Amazon spokesperson said. Ad units will appear as text or images beneath ChatGPT responses, they added.watch nowRead more CNBC tech newsApple event live updates: First foldable iPhone, new watch series expected as Ternus makes debutAndreessen- and Thiel-backed defense startup opens U.S. missile factory as it exits stealthAnthropic researcher says AI has more than 10% chance of 'killing all humans' after colleague quitsHow one hedge-fund manager built his firm to be powered entirely by AI agents