3-D ultrasound imaging is essential for accurate measurement of volumes, proper interpretation of anatomy, and guiding interventional procedures in the clinic. Furthermore, 3-D ultrasound imaging with a high volume rate is critical for advancing emerging techniques such as elastography, blood flow imaging, functional ultrasound (fUS) and super-resolution ultrasound localization microscopy from 2-D to 3-D. However, current 3-D ultrasound techniques are burdened by the low imaging volume rate of methods based on 1-D arrays, and the high fabrication and computational costs of 2-D arrays. Although some of the drawbacks can be mitigated by techniques such as row-column-addressing arrays, sparse arrays, and micro-beamforming, a viable solution that provides high imaging quality, low-cost, and high volume rates remains elusive. To address this challenge, this paper proposes a novel 3-D ultrasound imaging technique: Fast Acoustic Steering via Tilting Electromechanical Reflectors (FASTER). FASTER uses a water-immersible and fast-tilting microfabricated electromechanical mirror to steer ultrafast plane waves in the elevational direction to achieve large field-of-view (FOV) 3-D imaging at a high volume rate with conventional 1-D transducers. A wire phantom study using a 15 MHz transducer demonstrated that FASTER could provide spatially accurate 3-D images (48 degree or 20 mm range at 25 mm depth in the elevational direction) with a 500 Hz imaging volume rate, which has comparable imaging resolution with conventional 3-D imaging based on the mechanical translation of the 1-D transducers. A tissue-mimicking phantom study shows that FASTER provides a comparable contrast level with mechanical translation-based 3-D imaging. FASTER offers a unique solution providing high imaging volume rates, large FOVs, and low-cost 3-D imaging that can be conveniently implemented on existing clinical systems with few hardware or software modifications.