In this letter, a linearly polarized eighth-mode substrate integrated waveguide (EMSIW) resonator antenna that operates at 2.42 GHz and can be used for commercial wireless LAN applications has been proposed. In comparison to its SIW resonator counterpart, this structure is reduced to 1/8 of its size, while still retaining competent performance characteristics and simple design. The proposed structure has been simulated using CST MWS to obtain the frequency response and radiation characteristics. This EMSIW antenna has dominant resonant frequency at 2.42 GHz and radiates with a gain around 5 dBi. The effect of variation of ground plane width has been studied. The structure has been implemented on FR-4 substrate, and the simulated and measured results are in good agreement.