The mental radio is a fictional object that features prominently in the Golden Age and some later adventures of DC Comics superheroine Wonder Woman.
It was created by William Moulton Marston as an allegory for intuitive telepathy, or ESP, which he believed was a real phenomenon.
Although the character most frequently shown to broadcast distress calls via mental radio was Wonder Woman, typically in the form of an "electronic" word balloon with a tail emanating from her forehead, mental radio broadcasting was not originally considered a feature of her tiara but was instead something even Steve Trevor and Etta Candy could do, with electronic thought balloons similarly pointing at their foreheads.
Mental radios featured prominently in a plot by Nazi agent Fausta Grables to steal a device in order to eavesdrop on Wonder Woman and her companions.
By the later pre-Crisis adventures, only Wonder Woman was shown to possess a mental radio outside of Paradise Island, and it was installed in her invisible jet.