The hippocampus is crucial for spatial navigation and episodic memory formation. Hippocampal place cells exhibit spatially selective activity within an environment and have been proposed to form the neural basis of a cognitive map of space that supports these mnemonic functions. However, the direct influence of place cell activity on spatial navigation behavior has not yet been demonstrated. Using an ‘all-optical’ combination of simultaneous two-photon calcium imaging and two-photon optogenetics, we identified and selectively activated place cells that encoded behaviorally relevant locations in a virtual reality environment. Targeted stimulation of a small number of place cells was sufficient to bias the behavior of animals during a spatial memory task, providing causal evidence that hippocampal place cells actively support spatial navigation and memory. Display omitted •Two-photon optogenetics in VR enables targeted manipulation of place cell ensembles•Activating specific place cell ensembles drives their spatially associated behavior•Place cell stimulation inhibits endogenous place code expression and triggers remapping•Direct evidence for a causal role of place cells in spatial navigation Selective stimulation of a small number of hippocampal place cells in mice provides causal evidence that hippocampal place cells actively support spatial navigation and memory.