A consultant (from the Latin consultare means "to discuss" from which we also derive words such as consul and counsel) is a professional who provides advice in a particular area of expertise such as management, technology, communication, engineering or system analysis and design.

A consultant is an expert or a professional in a specific field and has a wide knowledge of the subject matter. A consultant works for a consultancy firm which has and engages with multiple and changing clients. Thus, clients have access to deeper levels of expertise than would be feasible for them to retain in-house. It is generally accepted good corporate governance to hire consultants as a check to the Principal-Agent problem by providing an outside expert view providing audit capability and a new set of eyes on solutions, processes and systems in a business".