A superconducting on-chip coiled coupled-line 90° hybrid coupler is made of a series array of repeated cells of coiled transmission lines that are inductively and capacitively coupled. The coupler splits an incoming microwave signal into two output signals of roughly equal power and separated in phase from each other by roughly 90°. The coupler can be incorporated into such superconducting electronic circuits as clock-distribution networks for reciprocal quantum logic (RQL) systems, as well as Josephson-based phase shifters and vector modulators.