An offboard circuit is one that is not connected to a main circuit board in an electronic system. For example, a computer graphics card is one of the components essential to the proper operation of the computer, but it is not directly attached to the motherboard like a RAM module or CPU.

The term may also apply to other, non-electronic systems such as closed-circuit rebreathers. Divers may refer to gas supplies that are detached from the main system as "offboard".

Electronics