The great practical utility has motivated extensive efforts to discover ultra-low resistance electrical conductors and superconductors in ambience. Here we report the observation of vanishingly small electrical resistance at the ambient temperature and pressure conditions in films and pellets of a nanostructured material that is composed of silver particles embedded into a gold matrix. Upon cooling below a sample-specific temperature scale ($T_{C}$) as high as $286$ K, the film resistance drops below $sim 2muOmega$, being limited by measurement uncertainty. The corresponding resistivity ($sim 10^{-12}$ $Omega$.m) is at least four orders of magnitude below that of elemental noble metals, such as gold, silver or copper. Furthermore, the samples become strongly diamagnetic below $T_{C}$, with volume susceptibilities as low as -0.056. We additionally describe methods to tune $T_{C}$ to temperatures much higher than room temperature.
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