A revenue stamp, tax stamp, duty stamp or fiscal stamp is a (usually) adhesive label used to designate collected taxes or fees on documents, tobacco, alcoholic drinks, drugs and medicines, playing cards, hunting licenses, firearm registration, and many other things. Typically, businesses purchase the stamps from the government (thereby paying the tax), and attach them to taxed items as part of putting the items on sale, or in the case of documents, as part of filling out the form.

Revenue stamps often look very similar to postage stamps, and in some countries and time periods it has been possible to use postage stamps for revenue purposes, and vice versa. Some countries also issued dual-purpose postage and revenue stamps.