A grow-op is a short term for a marijuana grow operation in which cannabis plants are grown in a (usually domestic) setting, usually with the intent of creating large amounts of marijuana for commercial purposes. The term may also apply to mass-growings of magic mushrooms. Although there are significant variations of climate in which cannabis can be cultivated, grow-ops will often make use of hydroponic technology to grow their plants indoors, and thus reduce the likelihood of detection.

In most countries, grow-ops are illegal, and are often disrupted by surprise police raids. It might not be coincidental that grow-ops are frequently rigged with booby traps to deter police and thieves alike.

Raiding a grow-op, for whatever purpose, can be a very risky endeavour, since for obvious reasons the operator may be far less hesitant to use violence or even deadly force to protect his or her operation.

In response, there have been calls for increased police resources to crush such operations with more vigor while others have called for ending marijuana prohibition to undercut the underground market that encourages these operations as was done with ending alcohol prohibition.