An infielder is a baseball or softball player whose position is in the infield, the area of dirt inside the diamond formed by the four bases. The four infield positions are first base, second base, shortstop (between second and third base), and third base.

Infielders need quick reflexes and sure hands because batted balls reach them fast, often in just a second or two. They have to field ground balls that bounce and hop unpredictably, catch line drives screaming toward them, and make accurate throws to get runners out. A good infielder can snag a hard grounder, pivot smoothly, and fire the ball to first base before the runner arrives.

Each infield position requires different skills. First basemen need to be good at catching throws from other infielders, even when those throws aren't perfect. Second basemen and shortstops cover the middle of the infield and often turn double plays together. Third basemen, playing the hot corner, face some of the hardest-hit balls in baseball and need strong arms to throw across the diamond to first base.

Compare this to outfielders, who play in the grassy area beyond the infield and chase down fly balls hit high and far.