AbstractWith conventional electronics reaching performance and size boundaries, all‐optical processes have emerged as ideal building blocks for high speed and low power consumption devices. A promising approach in this direction is provided by valleytronics in atomically thin semiconductors, where light‐matter interaction allows to write, store, and read binary information into the two energetically degenerate but non‐equivalent valleys. Here, nonlinear valleytronics in monolayer WSe₂ is investigated and show that an individual ultrashort pulse with a photon energy tuned to half of the optical band‐gap can be used to simultaneously excite (by coherent optical Stark shift) and detect (by a rotation in the polarization of the emitted second harmonic) the valley population.