The model of interacting fermion systems in one dimension known as a Tomonaga-Luttinger liquid (TLL)(1,2) provides a simple and exactly solvable theoretical framework that predicts various intriguing physical properties. Evidence of a TLL has been observed as power-law behaviour in electronic transport on various types of one-dimensional conductor(3-5.) However, these measurements, which rely on d. c. transport involving electron tunneling processes, cannot identify the longawaited hallmark of charge fractionalization, in which an injection of elementary charge e from a non-interacting lead is divided into the non-trivial effective charge e(star) and the remainder,e-e star (refs 6-8). Here, we report time-resolved transport measurements(9) on an artificial TLL composed of coupled integer quantum Hall edge channels(10), in which we successfully identify single charge fractionalization processes. A wave packet of charge q incident from a non-interacting region breaks up into several fractionalized charge wave packets at the edges of the artificial TLL, from which transport eigenmodes can be evaluated directly. These results are informative for elucidating the nature of TLLs and low-energy excitations in the edge channels(11).