A mutual fund is a professionally managed investment fund that pools money from many investors to purchase securities. While there is no legal definition of the term "mutual fund", it is most commonly applied to so-called open-end investment companies, which are collective investment vehicles that are regulated and sold to the general public on a daily basis.

Mutual funds may invest in many kinds of securities. The types of securities that a particular fund may invest in are set forth in the fund's prospectus, a legal document which describes the fund's investment objective, investment approach and permitted investments.