We report measurements of excess electron mobility in dense Argon gas at the two temperatures T = 152.15 and 162.30 K, fairly close to the critical one (T c = 150.7 K), as a function of the gas density N up to 14 atoms·nm −3 (N c = 8.08 atoms·nm −3 ). For the first time a maximum of the zero-field density-normalized mobility µ 0 N has been observed at the same density where it was detected in liquid Argon under saturated vapor pressure conditions. The existence of the µ 0 N maximum in the liquid is commonly attributed to electrons scattering off longwavelength collective modes of the fluid, while for the low-density gas a densitymodified kinetic model is valid. The presence of the µ 0 N maximum also in the gas phase raises therefore the question whether the single scattering picture valid in the gas is valid even at liquid densities.