Aquatic‐terrestrial amphibious robots are of significant value in various fields due to their exceptional environmental adaptability and multitask flexibility. However, existing designs often rely on complex limb configurations, multistructural modules, and collaborative mechanisms within the drive systems, which increase the complexity of both structure and control. Here, we present an origami‐inspired lightweight amphibious robot actuated by a single shape memory alloy (SMA), enabling efficient multimodal locomotion. A single degree‐of‐freedom rigid origami pattern with displacement amplification is first developed. Combined with anisotropic friction feet and an SMA actuator, this mechanism facilitates terrestrial crawling. By extending the origami pattern to form enclosed cavities, the robot achieves jet‐propelled swimming in aquatic environments. To further enhance locomotion versatility, an optimized design incorporating fan‐shaped units is introduced. Prefolded creases and vertex flipping in these units enable symmetry breaking, allowing effective adaptation across different motion modes. This work offers new insights into the development of lightweight, low‐power, and highly integrated amphibious robots that can operate in multiple environments.