We present the realization of an integrated electrical source of confined surface plasmon polaritons (SPPs) in metal-insulator-metal waveguides. Using an integrated light-emitting diode (LED) and subwavelength slits, we can couple light emitted by the LED directly into waveguided plasmon modes. Polarization-dependent measurements, decay length measurements, and spectral measurements are performed to confirm the electrical excitation of SPPs and characterize the properties of the plasmonic waveguide.