A plug electrical connector including a body and a plurality of cable terminals is provided. The body includes a top surface, two side surfaces opposite to each other, at least one locking slot, and a pair of locking protrusions. The top surface is bordered between the two side surfaces, the locking slot is located on the top surface, and the locking protrusions are located on the side surfaces. The cable terminals penetrate through the body and are arranged between the side surfaces in an axial direction. The plug electrical connector is adapted to be butted to a receptacle electrical connector and is engaged with the receptacle electrical connector with the locking slot and the locking protrusions. A receptacle electrical connector is also provided.