Two gay rights activists were among a group of nine Russian civil society members Obama briefly met just before taking off from Saint Petersburg after the two-day G20 summit hosted by President Vladimir Putin.
Speaking to the group at a hotel near the airport where his plane was waiting, Obama said he is "very proud" of the activists' work.
"The kinds of activities that are represented here are critically important to Russia's development," Obama said. The group also included defenders of business rights, environmentalists, and an investigative journalist from a Russian opposition paper.
"It's important to remember that in every country, here in Russia, in the United States, around the globe, that part of good government is making sure that we're creating space for civil society to function," Obama said.
This included ensuring "freedom of the press, freedom of assembly, and making sure that people can join together and make common cause around the issues that we care deeply about," he added.
Ahead of the event, gay activists told AFP they want it to be an "example for the Russian president," and hoped that they can raise awareness about discrimination against sexual minorities in the wake of a law Putin signed in June.