In astronomy, a light curve is a graph of light intensity as a function of time. The light is usually in a particular frequency interval or band.

Light curves can be periodic, as in the case of eclipsing binaries, cepheid variables and other variables, or aperiodic, like the light curve of a nova, a cataclysmic variable star or a supernova.

The study of the light curve, together with other observations, can yield considerable information about the physical process that produces it or constrain the physical theories about it.

In planetology, a light curve can be used to estimate the rotation period of a minor planet or moon. From the Earth, there is often no way to resolve a small object in our Solar System, even in the most powerful telescope. The size of the object is smaller than one pixel in the detector. Thus, astronomers measure the amount of light produced by an object as a function of time (the light curve). Looking for peaks in the light curve can produce estimates of the rotation rate of the object, assuming that there are parts of the object that are brighter or darker than average. In this case, there is sometimes aliasing, where it is unclear whether there is one or two light curve peaks per rotation period.