  Using the recently proposed covariant framework of general relativistic
stochastic mechanics and stochastic thermodynamics, we proved the detailed and
integral fluctuation theorems in curved spacetime. The time-reversal
transformation is described as a transformation from the perspective of
future-directed observer to that of the corresponding past-directed observer,
which enables us to maintain general covariance throughout the construction.
The result presented in this work may be applied in understanding the origin of
irreversibility in macroscopic processes in the presence of relativistic
gravity, as in most astrophysical or cosmological processes.
