Systems, methods, and sensor devices for fluid conduit inspection using passive magnetometry are provided. A method of inspecting a fluid conduit using passive magnetometry includes collecting magnetic flux data from inside the fluid conduit without actively magnetizing the fluid conduit, the magnetic flux data representing a residual magnetization of the fluid conduit, and identifying a conduit condition for the fluid conduit using the magnetic flux data. A computer system includes a memory for storing magnetic flux data collected from inside the fluid conduit without active magnetization of the fluid conduit, the magnetic flux data representing a residual magnetization of the fluid conduit; and a processor in communication with the memory and configured to generate an electronic representation of a conduit condition for the fluid conduit based on the magnetic flux data, wherein the electronic representation is stored in the memory.