Mg and its related solid base catalysts have always been thought of with weak or medium basicity. Herein, we present the synthesis of Mg single atom catalyst (Mg1/NPC) with strong basicity by tuning its coordination environment, which shows unusual activity in strong‐base‐catalyzed transesterification reaction. Mg1/NPC were obtained through impregnation‐pyrolysis method, results manifest Mg single atoms are embedded in nitrogen doped carbon in penta‐coordination (Mg‐C3N2) which endows Mg single atoms with strong basicity and is in contrast to traditional alkaline‐earth metal oxides. The novel Mg1/NPC exhibits excellent activity (40.2%) and stability in transesterification of methanol and ethylene carbonate to produce dimethyl carbonate (DMC), outperforming all state‐of‐the‐art Mg‐based solid base catalysts thus far reported as well as Ca, Na, and K‐based catalysts with superbasicity (2.5%–39.2%). This work might pave the way for the advancement of novel solid base catalysts with extraordinary sources of basicity for multifarious applications.