A latching actuator capable of repeated operation in a cryogenic, remote, or difficult-to-access environment, capable of enduring many cycles without user intervention or maintenance, capable of latching in a fixed position without consuming additional power, or to operate independent of external environmental conditions. In selected embodiments, a latching actuator may comprise an expansion chamber that houses a working substance capable of undergoing a phase change, a logic mechanism, a biasing assembly, and an output pin. In one embodiment, a wax motor may provide the motive force to toggle a latching mechanism. An actuator may be capable of positioning an output pin in two or more discrete latching positions and may be used to create a thermal connection between two structures, to engage or disengage a clutch, or to position an optical element in an optical instrument. An actuator may also be used as a launch lock apparatus.