The Monegasque was fastest in FP2, also, but that session was interrupted by several crashes, involving Max Verstappen, Bottas, and Sebastian Vettel.
In a much cleaner outing at the Red Bull Ring, Leclerc took advantage of the straights to finish with the quickest time, in a track which appeared to suit his Ferrari.
He set a time of 1:03.987 which was a tenth faster than Hamilton in second.
Vettel and Verstappen recovered from their spins in FP2 to finish fourth and fifth, while Lando Norris managed to split the Red Bulls with Pierre Gasly in seventh. The Frenchman was dogged by engine issues and complained of a lack of power at points.