In this letter, a new class of wideband phase shifters using parallel-coupled-line resonators is proposed and developed. The proposed phase shifter consists of two distinctive branches: a parallel-coupled-line filter and a reference line section. Compared with its conventional counterpart, this phase shifter has a few advantageous features such as simple geometry, small size, wide bandwidth, small phase deviation, and easy adjustment in phase shift. Then, a synthesis design method for a wideband phase shifter is described. For verification, its prototype circuit with a phase shift of 180° is finally designed, fabricated, and measured. Simulated and measured results are found in good agreement.