Ultrafast spatiotemporal control over the launch direction of surface plasmon polariton (SPP), which is highly desirable for the realization of integrated nanophotonic devices and ultrafast data processing systems within plasmonic nano-circuitry, remains a significant challenge. In particular, ultrafast spatial-temporal switching of SPP directional emissions in orthogonal directions has not yet been reported. Here, we propose a novel compact plasmonic nanoantenna structure design for spatiotemporal control of SPP launch at the nano−femto scale. This device possesses the capacity to launch the SPP directionally into different orthogonal output channels by changing the polarization direction of incident light. More importantly, ultrafast switching of the SPP directional launch at a femtosecond time scale has been proposed via adjusting the instantaneous polarization state of the excitation light. This study can lay the foundation for the development of miniaturized signal processing systems for high-speed data processing, and highly integrated nanophotonic devices, as well as for enhancing the functionality of next-generation optical nanocircuits.