Significance The excitation energy transfer in light-harvesting complexes is usually studied either by ultrafast bulk spectroscopy or by single-molecule spectroscopy. These methods are to a high degree complementary: Bulk spectroscopy measures ultrafast processes averaged over thousands of complexes, whereas single-molecule spectroscopy observes much slower dynamics in individual complexes. In this work, we combine these approaches using a recently developed ultrafast single-molecule spectroscopy technique. This enables us, for the first time (to our knowledge), to observe ultrafast energy relaxation with a rate around 100 fs in individual light-harvesting complexes. We determine the distribution of the relaxation times, observe changes of the relaxation time in one complex, and find how the relaxation depends on excitation wavelength.