Photonic elements can carry information with a capacity exceeding 1,000 times that of electronic components, but, due to the optical diffraction limit, these elements are large and difficult to integrate with modern-day nanoelectronics or upcoming packages, such as three-dimensional integrated circuits or stacked high-bandwidth memories1,2,3. Surface plasmon polaritons can be confined to subwavelength dimensions and can carry information at high speeds (>100 THz)4,5,6. To combine the small dimensions of nanoelectronics with the fast operating speed of optics via plasmonics, on-chip electronic–plasmonic transducers that directly convert electrical signals into plasmonic signals (and vice versa) are required. Here, we report electronic–plasmonic transducers based on metal–insulator–metal tunnel junctions coupled to plasmonic waveguides with high-efficiency on-chip generation, manipulation and readout of plasmons. These junctions can be readily integrated into existing technologies, and we thus believe that they are promising for applications in on-chip integrated plasmonic circuits.