Highly transparent lead-free (1-x)K0.5Na0.5NbO3-xSr(Zn1/3Nb2/3)O-3 (KNN-xSZN) ferroelectric ceramics have been synthesized via a conventional pressureless sintering method. All samples are optically clear, showing high transmittance in the visible and near-infrared regions (similar to 70% and similar to 80% at 0.5mm of thickness, respectively). This exceptionally good transmittance is due to the pseudo-cubic phase structure as well as the dense and fine-grained microstructure. In addition, a high energy storage density of 3.0J/cm(3) has been achieved for the 0.94K(0.5)Na(0.5)NbO(3)-0.06Sr(Zn1/3Nb2/3)O-3 ceramics with submicron-sized grains (similar to 136nm). The main reason is likely to be the typical relaxor-like behavior characterized by diffuse phase transition, in addition to the dense and fine-grained microstructure. This study demonstrates that the 0.94K(0.5)Na(0.5)NbO(3)-0.06Sr(Zn1/3Nb2/3)O-3 ceramic is a promising candidate of lead-free transparent ferroelectric ceramics for new areas beyond transparent electronic device applications.