The invention relates to a feedstock injector (2′) for injecting an atomized hydrocarbon feedstock into a tubular-type reactor with substantially upward or downward flow that is intended to be used in a fluid catalytic cracking unit, having: at least one hollow cylindrical body (41); at least a first and a second inlet openings (40, 42) for respectively injecting a liquid hydrocarbon feedstock to be cracked and an atomizing gas into said cylindrical body (41); at least one contact chamber (46) arranged inside said hollow cylindrical body, in which said liquid hydrocarbon feedstock to be cracked and said atomizing gas are intended to be brought into contact in order to atomize said liquid hydrocarbon feedstock to be cracked; and at least one outlet opening (44) that opens on the inside of said reactor in order to eject said liquid hydrocarbon feedstock thus atomized. According to the invention, each element of the injector (2′) is formed of a ceramic material.