Is your refrigerator a frost-free model, or does it have an automatic-icemaker water-connection?
Chances are either, Your refrigerator's:
1. Has a bad door-seal, and water is condensing & dripping - replace seal;
2. Automatic-icemaker water is leaking - fix/shut-off leak;
3. Is a frost-free model, and your condensate or evaporator drain is clogged & overflowing - unclog drain.