Citi is jumping into the ad business and entering a fast-growing and competitive market

Citi is the latest company outside Madison Avenue to launch an advertising business.

The bank exclusively told CMO Insider that it’s creating a new unit called Citi Commerce Media, which will let brands advertise to its more than 70 million customers based on their spending.

Citi will target ads to people on its own app and website, as well as on other properties, based on their spending histories. So a customer scrolling on Facebook could see a 10% off ad from a travel company, for instance.

Part of Citi’s pitch is that it can link its ads to measurable business impacts. It said it ran a pilot ad with retail, payments, technology, and health…