We derive the three-loop order renormalization group equations that describe the flat phase of polymerized membranes within the modified minimal subtraction scheme, following the pioneering one-loop order computation of Aronovitz and Lubensky [Phys. Rev. Lett. 60, 2634 (1988)] and the recent two-loop order one of Coquand, Mouhanna and Teber [Phys. Rev. E 101, 062104 (2020)]. We analyze the fixed points of these equations and compute the associated field anomalous dimension $\eta$ at three-loop order. Our results display a striking proximity with those obtained using nonperturbative techniques and re-expanded in powers of $\epsilon=4-D$. Moreover, the three-loop order value that we get for $\eta$ at the stable fixed point, $\eta=0.8872$, in $D=2$, is in quantitative agreement with known theoretical and numerical values.