This chapter introduces the ocean’s inherent renewable resource—wave energy. It traces the field from early inventions to today’s portfolio of devices, clarifying how each captures energy and where it is best sited. It is candid about the sector’s central dilemma: balancing survivability in raging seas with efficient energy capture, and how control strategies, materials, and power-conversion choices navigate that trade-off. Case studies and actor maps illustrate progress and bottlenecks, highlighting the pathway from prototypes to bankable, large-scale arrays.