<p>Residual stresses generated during machining directly influence the dimensional accuracy and functional performance of the manufactured part. Unlike turning, milling involves repeated engagement and disengagement between the tool and the workpiece, producing a unique stress state on the machined surface. These residual stresses are mainly caused by the combined action of mechanical loading and thermal input during cutting. This phenomenon is enhanced in Inconel 718 because of its high strength and low thermal conductivity, which makes it difficult to machine; it therefore has a strong position among those alloys used for aerospace and automotive applications. This present study examines the formation of residual stresses in high-speed milling of Inconel 718 using a combination of numerical and experimental approaches. Initially, a two-dimensional finite element model using the Johnson–Cook constitutive law and damage formulations is used to characterize the material response under severe machining conditions. Secondly, the results of the simulation are verified with the experimental data of cutting forces, temperature development, and chip morphology, and a good agreement is found. Thirdly, after machining, the workpiece is then allowed to reach thermal equilibrium at ambient temperature, and the residual stresses are determined. Lastly, the effects of cutting speed and feed rate on the residual stresses are studied, and subsurface nano-hardness is determined using nanoindentation. The results show that elevating cutting speeds tends to favor compressive residual stresses, while a lower feed rate is responsible for a better stress state.</p>