Inflationism is a heterodox economic, fiscal, or monetary policy, that predicts that a substantial level of inflation is harmless, desirable or even advantageous. Similarly, inflationist economists advocate for an inflationist policy.

Mainstream economics holds that inflation is a necessary evil, and advocates a low, stable level of inflation, and thus is largely opposed to inflationist policies – some inflation is necessary, but inflation beyond a low level is not desirable. However, deflation is often seen as a worse or equal danger, particularly within Keynesian economics, as well as Monetarist economics and in the theory of debt deflation.

Inflationism is not accepted within the economics community, and is often conflated with Modern Monetary Theory, which uses similar arguments, especially in relation to chartalism.

In political debate, inflationism is opposed to hard currency, which believes that the real value of currency should be maintained.

In late 19th century United States, the Free Silver movement advocated the inflationary policy of free coinage of silver. This was a contentious political issue in the 40-year period 1873–1913, consistently defeated. Later, economist John Maynard Keynes described the effects of inflationism:

Lenin is said to have declared that the best way to destroy the capitalist system was to debauch the currency. By a continuing process of inflation, governments can confiscate, secretly and unobserved, an important part of the wealth of their citizens. By this method they not only confiscate, but they confiscate arbitrarily; and, while the process impoverishes many, it actually enriches some. The sight of this arbitrary rearrangement of riches strikes not only at security but [also] at confidence in the equity of the existing distribution of wealth.

Those to whom the system brings windfalls, beyond their deserts and even beyond their expectations or desires, become "profiteers," who are the object of the hatred of the bourgeoisie, whom the inflationism has impoverished, not less than of the proletariat. As the inflation proceeds and the real value of the currency fluctuates wildly from month to month, all permanent relations between debtors and creditors, which form the ultimate foundation of capitalism, become so utterly disordered as to be almost meaningless; and the process of wealth-getting degenerates into a gamble and a lottery.

Lenin was certainly right. There is no subtler, no surer means of overturning the existing basis of society than to debauch the currency. The process engages all the hidden forces of economic law on the side of destruction, and does it in a manner which not one man in a million is able to diagnose.