There have been Groupons for Botox, airfare, and even NBA tickets. And soon, Chicago Transit Authority passes.

More than 530 million people used Chicago Transit last year. But the CTA hopes a Groupon for its three-day passes it announced Tuesday will bring in new riders.

The conversations between the transit agency and the Chicago-based internet deal company started a few months ago, spokesman Brian Steele said. That’s when the CTA decided to focus the deal on its three-day passes, which usually cost $14.

“We find that we sell three-day passes in most of the areas frequented by tourists,” Steele said, adding most of 600,000 such passes sold last year were at the airport, along Michigan Avenue and in Millennium Park.

The deal is the first Groupon has offered with any transit agency in the U.S., Steele said.

The Groupon will offer the three-day pass for $9. The CTA will receive an upfront payment of $1.88 million for the deal, which so far involves 250,000 passes that the CTA is selling to Groupon for $7.53 each.

Steele took care to point out those 250,000 were “over and above” what the CTA expects to sell this year, another 600,000 passes.

The plan is to offer the Groupon in a national deal by the end of the month. Groupon is expected to advertise the offer through its Getaways section that also offers deals on hotels and travel.

If it goes well, the deal includes an option to sell another 250,000 passes within the next 12 months.