We discovered that Knifefish (Apteronutus albifrons) can generate cavitation bubbles using a powerful rapid suction while feeding from a capillary tube. In this way, knifefish can draw a potent jet of water into the mouth that is ~450 Gs (acceleration due to gravity). Cavitation Number calculated on flow acceleration was less than one (average Ca ~ 0.65), which indicates cavitation occurrence. Furthermore, when fish were allowed to suction feed from a capillary tube sealed at one end, we observed large cavitation bubbles appear and collapse in less than 22 ms. A hammer-like sound was recorded, which coincides with bubble collapse. DPIV measurements indicate that knifefish can generate a ~ 3 mm suction range with flow speeds up to 2.5 m/s in less than one millisecond. We suggest that cavitation may serve knifefish in the immobilization, dislodgement, and capture of prey, as well as a detection method for small prey hidden in narrow refuges. Thus, cavitation exploitation may be more widespread among suction-feeding organisms than has been previously thought.