A bicycle derailleur includes a fixing member, a selected chain guide unit and a motor unit. The fixing member is configured to be fixed to a bicycle frame. The selected chain guide unit has a chain guide for guiding a bicycle chain and a support mechanism moveably supporting the chain guide relative to the fixing member. The selected chain guide unit is one of a plurality of different configurations of chain guide units. The motor unit is configured to be selectively attached to the selected chain guide unit to move the chain guide. The motor unit is configured to be mounted to each of the plurality of configurations of chain guide units.