Abstract: A traversing blade rotary propeller useful as a propulsion system for various types of boats and aircraft or as a wind or water actuated turbine. A traversing blade rotary propeller of this type includes a stationary main shaft, a mount to which an end of the stationary main shaft is affixed, a central housing structured to carry a pair of alternately disposed, perpendicularly projecting radial arm shafts, and where the device is used as a propulsion system, power means for rotation of said central housing relative to the fixed axis formed by said stationary main shaft. A pair of propeller shafts extend perpendicularly from an end of each of said radial arm shafts, and flat propeller blades are attached to each. The inboard ends of each of the radial arm shafts are operatively engaged with the stationary main shaft, and the outboard ends are operatively engaged with the propeller shafts, as via gears such that rotation of the central housing produces rotation of the propeller shafts.