A capital market is a financial market in which long-term debt (over a year) or equity-backed securities are bought and sold, in contrast to a money market where short-term debt is bought and sold. Capital markets channel the wealth of savers to those who can put it to long-term productive use, such as companies or governments making long-term investments. Financial regulators like Securities and Exchange Board of India (SEBI), Bank of England (BoE) and the U.S. Securities and Exchange Commission (SEC) oversee capital markets to protect investors against fraud, among other duties.

Transactions on capital markets are generally managed by entities within the financial sector or the treasury departments of governments and corporations, but some can be accessed directly by the public. As an example, in the United States, any American citizen with an internet connection can create an account with TreasuryDirect and use it to buy bonds in the primary market. However, sales to individuals form only a small fraction of the total volume of bonds sold. Various private companies provide browser-based platforms that allow individuals to buy shares and sometimes even bonds in the secondary markets. There are many thousands of such systems, most serving only small parts of the overall capital markets. Entities hosting the systems include investment banks, stock exchanges and government departments. Physically, the systems are hosted all over the world, though they tend to be concentrated in financial centres like London, New York, and Hong Kong.

A capital market can be either a primary market or a secondary market. In a primary market, new stock or bond issues are sold to investors, often via a mechanism known as underwriting. The main entities seeking to raise long-term funds on the primary capital markets are governments (which may be municipal, local or national) and business enterprises (companies). Governments issue only bonds, whereas companies often issue both equity and bonds. The main entities purchasing the bonds or stock on primary markets include pension funds, hedge funds, sovereign wealth funds, and less commonly wealthy individuals and investment banks trading on their own behalf. In the secondary market, existing securities are sold and bought among investors or traders, usually on an exchange, over-the-counter, or elsewhere. The existence of secondary markets increases the willingness of investors in primary markets, as they know they are likely to be able to swiftly cash out their investments if the need arises.

A second important division falls between the stock markets (for equity securities, also known as shares, where investors acquire ownership of companies) and the bond markets (where investors become creditors).

The money markets are used to raise short-term finance; including loans that are expected to be paid back as early as overnight. In contrast, the "capital markets" are used to raise long-term finance, in the form of shares/equities, and loans that are not expected to be fully paid back for at least a year.

Funds borrowed from money markets are typically used for general operating expenses, to provide liquid assets for brief periods. For example, a company may have inbound payments from customers that have not yet cleared, but need immediate cash to pay its employees. But when a company borrows from the primary capital markets, often the purpose is to invest in additional physical capital goods, which will be used to help increase its income. It can take many months or years before the investment generates sufficient return to pay back its cost, and hence the finance is long term.

Together, money markets and capital markets form the financial markets, as the term is narrowly understood. The capital market is concerned with long-term finance. In the widest sense, it consists of a series of channels through which the savings of individuals and institutions are made available for industrial and commercial enterprises and public authorities. This process of channeling savings into productive investments is crucial for economic growth and development. Moreover, capital markets provide opportunities for both individuals and institutions to diversify their investments, thereby managing risk and potentially enhancing returns over the long term.

Normal bank lending is not usually classed as a capital market transaction, even when loans are extended for a period longer than a year. First, these bank loans are not securitized (i.e. they are not packaged into a resaleable security like a share or bond that can be traded on the markets). Second, lending by banks is more heavily regulated than capital market lending. Third, bank depositors tend to be more risk-averse than capital market investors. These three differences all act to limit institutional lending as a source of finance. Two additional differences, this time favoring lending by banks, are that banks are more accessible for small and medium-sized companies, and that they have the ability to create money as they lend. In the 20th century, most company finance apart from share issues was raised by bank loans. But since about 1980 there has been an ongoing trend for disintermediation, where large and creditworthy companies have found they effectively have to pay out less interest if they borrow directly from capital markets rather than from banks. The tendency for companies to borrow from capital markets instead of banks has been especially strong in the United States. According to the Financial Times, capital markets overtook bank lending as the leading source of long-term finance in 2009, which reflects the risk aversion and bank regulation due to the 2008 financial crisis.