In this article, a new class of wideband phase shifters with very compact size, large phase shift value, low insertion loss (IL), and low cost are presented and developed. The proposed phase shifter consists of N series and shunt resonators, which can achieve the magnitude and phase shift bandwidth of more than 120% thanks to N transmission poles. Besides the wideband property, the proposed phase shifter is able to achieve a small size of nearly 1/10 guided wavelength (λg), which has a size reduction of more than 90% as compared with conventional wideband phase shifters on printed circuit board (PCB). Meanwhile, insertion phases for the both series and shunt resonators are zero at their resonant frequencies; thus, the length of reference line can be also greatly reduced. What is more, a detailed synthesis method with closed-form equations is presented and employed to determine all circuit parameters of the proposed phase shifter with the specified in-band return loss (RL), phase shift value AΦ, and resonator number N. To validate the design concept, three design examples of 90° and 180° phase shifters on N = 3 and N = 5 are synthesized and tested. Theoretical, simulated, and measured results are in a fairly close agreement. In particular, the proposed phase shifters feature very low IL. The measured maximum in-band IL is only 0.38 dB for N = 3 (AΦ = 90°) and 0.50 dB for N = 5 (AΦ = 180°).