What is the ruling on monopolising or hoarding essential goods to drive up prices?

Summary

Monopoly of goods (al-ihtikar) means buying and hoarding staple foods when people need them, then selling them gradually at greatly inflated prices. The practice is forbidden based on a hadith reported by Muslim, because it harms the public. In times of urgent need or emergency, the hoarder may be compelled to sell at a reasonable price, and a judge may sell on his behalf if he refuses. Buying in season when goods are plentiful, to store and resell when needed such as food stockpiling, is not monopoly and is permitted.

Written in our own words from the original fatwa — check the source before acting on it.