Liquid Mg is capable of quickly eroding the refractory Ni-based superalloy and selectively dissolve Ni, which opens up a new avenue for the recycling of superalloy scraps for comprehensive metal reclamation. This study aims at investigating the underlining mechanism and kinetics of the selective dissolution of Ni from Inconel 718 (one type of Ni-based superalloy) with liquid Mg, by experimenting at 750, 800, and 850 °C for various amounts of time in an inert atmosphere. This selective dissolution process is also known as liquid metal dealloying. Results show that a permeable dealloyed layer was formed resulting from the preferential dissolution of Ni over other metallic elements (e.g., Fe, Cr, Nb, Mo, and Ti). At the dealloying forefront, the grain boundaries of the matrix γ phase were preferentially eroded by liquid Mg. The opposite concentration gradients of Ni (4–9 wt%) and Mg (12–18 wt%) cross the dealloyed layer suggested their counter diffusion. A higher heating temperature substantially increased the dealloying rate. Graphical Abstract: [Figure not available: see fulltext.] © 2022, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.