A distilled water dielectric resonator antenna (DRA) with a wide frequency-tuning range and high efficiency is presented in this article. It consists of a water resonator and a ground plane with a wideband bowtie feeding slot. The water resonator, having tunable dimensions, is employed to achieve frequency-reconfigurable characteristics. Mechanical switches and a microfluid pump are integrated to control the tuning process. The water DRA, with and without the liquid control system, is designed with a simulation tool and then fabricated and measured to validate the antenna's performance. It is demonstrated that the antenna exhibits high total efficiency (> 80%) across a wide frequency-tuning range from 168 to 474 MHz (for S11, -10 dB) with a very compact volume of 278 × 278 × 131 mm3 (0.155λ × 0.155m × 0.073m at 168 MHz). Compared with traditional reconfigurable antennas, this design provides a wider frequency-tuning range, a more compact size, and a higher degree of design freedom. It is therefore a promising candidate for very high-frequency (VHF) and ultrahigh-frequency (UHF) applications.