Urban exploration (often shortened as urbex, UE, bexing, urbexing and sometimes known as 'roof-and-tunnel hacking') is the exploration of man-made structures, usually abandoned ruins or not usually seen components of the man-made environment. Photography and historical interest/documentation are heavily featured in the hobby and, although it may sometimes involve trespassing onto private property, this is not always the case. Urbex (or urban exploration may also be referred to as draining (an alternate form of urbexing where drains are explored), urban spelunking, urban rock climbing, urban caving, roof topping or building hacking.

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The nature of this activity presents various risks, including both physical danger and the possibility of arrest and punishment. Some activities associated with urban exploration may violate local or regional laws and certain broadly interpreted anti-terrorism laws or be considered trespassing or invasion of privacy.