A registered investment adviser (RIA) is a firm that is an investment adviser in the United States, registered as such with the Securities and Exchange Commission (SEC) or a state's securities agency. The numerous references to RIAs within the Investment Advisers Act of 1940 popularized the term, which is closely associated with the term investment adviser. An investment adviser is defined by the Securities and Exchange Commission as an individual or a firm that is in the business of giving advice about securities. However, an RIA is the actual firm, while the employees of the firm are called Investment Adviser Representatives (IARs).

Registered investment adviser firms receive compensation in the form of fees for providing financial advice and investment management. They are required to act as a fiduciary. This is very different from broker-dealers and their representatives, who provide recommendations for a commission. Broker-dealers and their representatives are not required to act as a fiduciary, they simply must make suitable recommendations for a client. This is a different standard of care, but most consumers are unaware of the difference, as any of these professionals may call themselves a financial advisor.

In some instances a firm may be "dual registered", meaning they are a registered investment adviser along with being registered as a broker-dealer. In that case they may provide advice for a fee and collect a commission on certain product sales.