Devices, systems, and methods are provided for magnetic focus enhanced lateral flow assays. The devices and systems are ultrasensitive and provide for the visual detection of the presence or absence of one or more target analytes—which may include pathogens, proteins, or even molecules smaller than the foregoing—even when such analytes are only present in very limited amounts. The devices and systems include an immunostrip with a magnet positioned adjacent thereto, and magnetic probes specific to a target analyte that bind to the target analyte with specificity if present within a fluid sample to be tested. Methods are also provided for detecting one or more target analytes using magnetic focus, such methods including a step of controlling movement of a target analyte complex on an immunostrip incorporating a magnetic field, where such control slows a flow of the target analyte complex through a capture area on the immunostrip.