A key platform technology for InP optical waveguide MEMS is developed. The novel waveguide design is entirely released from the substrate by sacrificial etching and the suspended waveguide is supported by lateral tethers. This allows free-standing, movable segments of waveguide while preventing substrate leakage loss in fixed segments of the waveguides. The optical, mechanical, and material design process is presented. A single-mask fabrication process is developed that can be extended to more complex devices employing electrostatic actuation. Relative power and Fabry-Perot contrast measurements indicate the fabricated suspended waveguides exhibit a propagation loss of 2.2 dB/cm and tethers induce 0.24 dB additional loss per pair. Future optical MEMS devices built with suspended InP waveguides are briefly introduced.