In this brief, a novel bandpass filter (BPF) with ultra-wide upper stopband performance is proposed and implemented on gallium arsenide (GaAs) integrated passive device (IPD) technology. Firstly, the proposed BPF is designed by introducing a <inline-formula> <tex-math notation="LaTeX">$\boldsymbol{\pi }$ </tex-math></inline-formula>-section to achieve an ultra-wide upper stopband. Following that, the working principle of achieving this ultra-wideband upper stopband performance is further investigated. Finally, to demonstrate the claimed performances, this BPF with a size of <inline-formula> <tex-math notation="LaTeX">$1.63 {\mathrm {\times }}0.62$ </tex-math></inline-formula> mm <sup>2</sup> has been fabricated on GaAs IPD technology and measured by on-wafer probing. The measured BPF with a 3-dB fractional bandwidth (FBW) of 95.3% (1.7-4.8 GHz), exhibits the expected performances, especially the superior upper stopband suppression level better than 20 dB until 110 GHz (34.6 <inline-formula> <tex-math notation="LaTeX">${f} _{0}$ </tex-math></inline-formula>). The simulated and measured results of the BPF are in reasonably good agreement, thus firmly validating the claimed superior performances of the BPF in terms of good frequency selectivity and ultra-wide upper stopband.