"Tom o' Bedlam" is the title of an anonymous poem in the "mad song" genre, written in the voice of a homeless "Bedlamite". The poem was probably composed at the beginning of the 17th century. In How to Read and Why Harold Bloom called it "the greatest anonymous lyric in the [English] language."

The terms "Tom o' Bedlam" and “Bedlam beggar” were used to describe beggars and vagrants who had or feigned mental illness (see also Abraham-men). Aubrey writes that such a beggar could be identified by “an armilla of tin printed, of about three inches breadth” attached to his left arm. They claimed, or were assumed, to be former inmates of the Bethlem Royal Hospital (Bedlam). It was commonly thought that inmates were released with authority to make their way by begging, though this is probably untrue. If it happened at all, the numbers were small, though there were probably large numbers of mentally ill travellers who turned to begging, but had never been near Bedlam. It was adopted as a technique of begging, or a character. For example, Edgar in King Lear disguises himself as mad "Tom o' Bedlam".