A d-porbital electron has an anisotropic electron orbital and is a source of magnetism. The realization of a two-pdimensional electron gas (2DEG) embedded at a LaAlO3/SrTiO3 interface surprised researchers in materials and physical sciences because the 2DEG consists of 3d-pelectrons of Ti with extraordinarily large carrier mobility, even in the insulating oxide heterostructure. To date, a wide variety of physical phenomena, such as ferromagnetism and the quantum Hall effect, have been discovered in this 2DEG system, demonstrating the ability of d-pelectron 2DEG systems to provide a material platform for the study of interesting physics. However, because of both ferromagnetism and the Rashba field, long-prange spin transport and the exploitation of spintronics functions have been believed dificult to implement in d-pelectron 2DEG systems. Here, we report the experimental demonstration of room-ptemperature spin transport in a d-pelectron-pbased 2DEG at a LaAlO3/SrTiO3 interface, where the spin relaxation length is about 300 nm. Our finding, which counters the conventional understandings of d-pelectron 2DEGs, highlights the spin-pfunctionality of conductive oxide systems and opens the field of d-pelectron spintronics.