This work proposes an ultralow scattering frequency selective rasorber (FSR) with a wide passband. By integrating absorption and phase cancellation mechanisms, a radar cross section reduction (RCSR) of over 20 dB is achieved across a wide frequency range. First, using array theory, the reflection characteristics of the unit cell that achieves a 20 dB RCSR for the array are derived. The impact of the unit cell on the array’s transmission characteristics is also investigated. Second, an FSR configuration is developed utilizing the equivalent circuit model (ECM). To achieve a lower Q-factor, a miniaturized wire grid for the interdigital resonator is placed on the backside. Third, a reflection phase difference is introduced between unit cells via a quarter-wavelength spacing, effectively integrating the two reduction mechanisms in an FSR array. Finally, a prototype is manufactured and measured, with experimental results aligning closely with simulations and confirming an RCSR greater than 20 dB in a broad frequency range of 2.95 to 9.10 GHz, corresponding to a relative bandwidth (RBW) of 102.07%. Furthermore, a stable wide passband is observed for incidence angles up to 45°. This work demonstrates superior RCSR performance compared to existing FSR designs reported in the literature.