In　this　letter,　a　GaAs-based　wideband　spoof　surface　plasmon　polariton　(SSPP)　waveguide　with　super　compact　size　is　presented　at　millimeter-wave　regime.　The　periodic　SSPP　unit　cell　consists　of　a　longitudinal　slot　and　a　meander　slot　in　transversal　direction,　and　its　corresponding　waveguide　has　good　low-pass　filtering　feature.　The　momentum　of　microstrip　line　for　measurement　feeding　to　the　SSPPs　can　be　well　matched　without　any　gradient　transition　structures.　To　apply　this　SSPP　waveguide　into　the　design　of　bandpass　filter　(BPF),　a　row　of　vias　is　added　with　a　certain　distance　from　the　SSPP　unit　cells.　For　demonstration,　two　on-chip　examples,　i.e.,　SSPP　waveguide　and　SSPP-based　BPF,　are　fabricated　operating　at　different　frequencies.　Good　agreement　between　simulations　and　measurements　validates　the　propagation　characteristics　and　implementation　of　the　proposed　SSPPs.　©　1989-2012　IEEE.