"30 Days in the Hole" is the seventh single by English rock group Humble Pie, from the band's 1972 Smokin' album. The song received moderate radio airplay at the time but failed to chart. However it gained a following on album oriented rock and classic rock radio formats and consequently it remains one of Humble Pie's best known songs.

The B-side on its US release was "Sweet Peace and Time", while everywhere else the B-side featured "C'mon Everybody" and "Road Runner".

The song, a Steve Marriott composition, bemoans being arrested for possession of small quantities of illegal drugs, including cocaine; Durban poison, a potent strain of marijuana, and Red Lebanese and Black Nepalese, two types of hashish. "New Castle Brown" is often mistaken as a reference to Newcastle Brown Ale but actually refers to heroin also known as "Brown" or "Smack". The song refers to Borstal - "some seeds and dust, and you got Borstal"- referring to Borstal Prison and its borstal ilk - any manner of a British juvenile gaol. (Most lyrics listings get this wrong, and say "buzzed on" or "bust on".)

Pie guitarist Clem Clempson has said it is one of the tracks he would most like his career to be remembered by. But the predominant group personality shown through by the song is Marriott's; so much so that for example when years later Clempson was asked about efforts to reform the group without Marriott, he simply declaimed, "It's a waste of time."

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