Goal-directed spatial navigation requires accurate estimates of one’s position and destination, but these estimates are still not sufficient. An animal is often required to plan a navigational route because a direct path to the goal is not necessarily available. Despite its importance, the neural circuits supporting route planning ability remain poorly understood. Previous studies have implicated the orbitofrontal cortex in representing an animal's destination, and the hippocampus in representing its own position as well as goal-directed paths. We hypothesize that interactions between these regions, mediated by the thalamic nucleus reuniens (RE), are critical for planning navigational routes. To test this hypothesis, we used a navigation task in which rats were required to take obstacle avoidance routes to a given destination without relying on sensory cues under minimum light conditions. Optogenetic silencing of the RE resulted in impairment of the animal’s route planning ability as it took a longer non-smooth path but correctly reached a goal location, highlighting a specific role of the RE in route planning but not goal recognition. Recordings from CA1 neuronal activity revealed that obstacle avoidance routes were represented by their brief sequential spiking or replay when the animal was at the starting position, but these representations were largely abolished by RE silencing. Our results together point to the key role of the RE in driving hippocampal replay sequences to sweep future goal-directed routes, supporting the animal’s ability to navigate to a desired destination by avoiding known obstacles in the environment.