Which small crater was Opportunity inside when it landed on Mars?

Opportunity was inside Eagle crater when it landed on Mars.

The rover touched down in Meridiani Planum on January 25, 2004, after bouncing and rolling inside its airbag cocoon. It came to rest in a small impact crater about 22 meters across—an astonishingly fortunate landing because the mission team had not targeted that crater specifically.

Scientists jokingly described the event as a “hole in one.” The crater was later named Eagle, a reference that connected the site with Apollo 11's lunar module, the United States emblem, and the golf metaphor. The landing site was also designated Challenger Memorial Station.

Eagle crater immediately became scientifically valuable. Its exposed rock layers and soil contained evidence that Meridiani Planum had once experienced acidic, salty water. Opportunity later drove out of Eagle and investigated the much larger Endurance, Victoria, and Endeavour craters, which are common sources of mix-ups in this question.