顾问(源自拉丁语:consultare意为“深思熟虑”)是在某一专门领域提供建议和其他有目的活动的专业人士(也称为专家、专家，见下文含义变化)。
咨询服务通常属于专业服务的范畴。
英国咨询公司将这一角色定义为“在特定的科学或商业领域为组织或个人提供专业或专家建议的人”。
哈佛商学院(Harvard Business School)对顾问给出了更具体的定义，即“如何在某一专业领域内修改、推进或简化特定流程”的顾问。
Alan Weiss在他的《咨询圣经》一书中定义:“当我们(咨询师)离开客户时，客户的状况应该比我们来之前或我们失败之前更好。”“顾问”这个头衔没有法律保护。
顾问的角色
医疗领域以外的顾问(该词专指医生职级)的作用可分为以下两类:
内部顾问:受雇于客户组织或与客户组织签订合同，并在客户组织内运营的人(可能是内部咨询部门的一部分);或外部顾问:由客户外部聘用的人(咨询公司、其他机构或独立自由职业者)，其专业知识作为合同的一部分提供，并收取费用或费率。
雇佣顾问的商业案例
传统上，通过雇用顾问，客户可以获得比他们长期留在公司内经济上可行的更高级别的专门知识。此外，客户可以通过向外部顾问购买自己想要的服务来控制自己的咨询服务支出。此外，顾问是具有特定领域技能的关键人员，包括制定战略、领导变革(如数字化)、领导培训、临时人员。
A consultant (from Latin: consultare "to deliberate") is a professional (also known as expert, specialist, see variations of meaning below) who provides advice and other purposeful activities in an area of specialization.
Consulting services generally fall under the domain of professional services.
Consultancy UK defines the role as a "person who provides professional or expert advice in a particular field of science or business to either an organisation or individual".
The Harvard Business School provides a more specific definition of a consultant as someone who advises on "how to modify, proceed in, or streamline a given process within a specialized field".
In his book, The Consulting Bible, Alan Weiss defines that "When we [consultants] walk away from a client, the client's conditions should be better than it was before we arrived or we've failed." There is no legal protection given to the job title 'consultant'.
Role of
a consultant
The role of consultant outside the medical sphere (where the term is used specifically for a grade of doctor) can fall under one of two general categories:
· Internal consultant: someone who is either employed by or contracted by a client organization, and operates within a client-organization (maybe as part of an internal consultancy unit); or
· External consultant: someone who is employed externally to the client (either by a consulting firm, some other agency or as an independent freelancer), whose expertise is provided as part of a contract for a fee or rate.
Business case for hiring a consultant
Traditionally, by hiring a consultant, clients acquire access to higher grades of expertise than would be financially feasible for them to retain in-house on a long-term basis. Moreover, clients can control their expenditures on consulting services by only purchasing as much services from the outside consultant as desired. Additionally, consultants are key persons with specific domain-skills in creating strategies, leading change (e.g. digitalization), leadership coaching, interim management (also called consultant manager), etc.