In a backlight assembly and a flat panel display apparatus, the backlight assembly has a diffusing plate, a supporting member and a reflecting plate. The supporting member has a base body portion, a supporting portion supporting the diffusing plate and a lamp holder receiving lamps to uniformly maintain spaced intervals between the lamps. The base body portion is disposed under the reflecting plate. The supporting portion and the lamp holder are inserted through engaging openings formed at the reflecting plate such that the supporting portion and the lamp holder are upwardly protruded with respect to the reflecting plate. Accordingly, the backlight assembly may reduce an area of the reflecting plate covered by the supporting member, thereby providing the light having uniform brightness distribution.