A slush fund is a fund or account used for miscellaneous income and expenses, particularly when these are corrupt or illegal. Such funds may be kept hidden and maintained separately from money that is used for legitimate purposes. Slush funds may be employed by government or corporate officials in efforts to pay influential people discreetly in return for preferential treatment, advance information (such as non-public information in financial transactions), and other services. The funds themselves may not be kept secret but the source of the funds or how they were acquired or for what purposes they are used may be hidden. Use of slush funds to influence government activities may be viewed as subversive of the democratic process.

A slush fund can also be a reserve account used to reduce fluctuations in an organization's earnings by withholding them when they are high and supplementing them when they are low. This type of slush fund is not inherently corrupt, but is nonetheless a form of earnings management that tends to mislead the public about the organization's financial condition.