A new spatial-axis toroidal stellarator is proposed and its basic properties are discussed. In basic concept, the stellarator is defined by a magnetic axis consisting of a double-helix transform-producing section, closed by half-torus turning sections at each end which produce little or no transform. Vacuum toroidal rotational transform and average magnetic well in straight double helices are similar to familiar purely helical systems. Vacuum magnetic-field calculations demonstrate closed three-dimensional magnetic surfaces in simple examples without well.