Napoleon’s famous proclamation that “an army marches on its stomach” might be applied to the operations of terrorist organizations. Shadowy and fearsome they might be, but they still must eat, drink, clothe and equip themselves, and be able to pay for their logistical and other needs. If counter-terrorism (CT) efforts can break terrorist financing, this can break the organization. This chapter explores the value of counter-terrorist financing (CFT), outlining its importance and then identifying four typologies, based on revenue origin, which help us to understand terrorist funding. It will look at two illustrative case studies (one on the operations of al-Qaeda in Iraq and the other on the use of gemstones in terrorist financing) and concludes by surveying money laundering operations and emerging trends in terrorist financing in the digital age.