A real estate broker is a party who acts an intermediary between sellers and buyers of real estate and attempts to find sellers who wish to sell and buyers who wish to buy.

In the United States, the relationship was originally established by reference to the English common law of agency with the the broker having a fiduciary relationship with his clients.

Real estate brokers and their salespersons (commonly called "real estate agents") assist sellers in marketing their property and selling it for the highest possible price under the best terms. When acting as a Buyer's agent with a signed agreement, they assist buyers by helping them purchase property for the best possible price under the best terms. Without an agreement, brokers may assist buyers in the acquisition of property but still represent the seller and the seller's interests.

In many jurisdictions, particularly those in the United States, a person is required to have a license in order to receive remuneration for services rendered as a real estate broker. In particular, any of the following descriptions could refer to a real estate broker in the USA:

• A licenced person owning, managing, or being in charge of a real estate brokerage firm, even if the broker just works for him- or herself.

• The real estate brokerage itself: the brokerage is the firm or business of the broker which can also be called a real estate agency.

• A licensed real estate professional who has obtained a broker's license (which entitles them to operate a real estate brokerage). By default, a real estate broker of this kind has already met the requirements of "salesperson" or "agent" licensure. A real estate broker can still be designated as such without owning a real estate brokerage.

• Some people may refer to any licensed real estate agent as a real estate broker. However, a licensed real estate agent is a professional who has obtained either a real estate salesperson's license or a real estate broker's license.