专业人士，通称专家、学者，即职场上的专门行业，指具备专业化知识及技能，并且以此为生的职业人士。通常，专业技能须符合科学原理，经过长时间的学习及训练，并有经考试获得的认证书或牌照，拥有自我约束行为的职业操守（或道德）及可量化的专业标准等。例如“风水师”就不属于专业人士，因其“专业标准”无法量化。相反的：一般的工程师在取得其工程师执照前，其训练过程皆需要有纪录可以追寻；而他们成为工程师之后，不单可以运用其专业知识为企划签字批准确认，其专业知识亦足以在法庭上以「专家证人」的成份为法庭提供专业判断证供。

A professional is a member of a profession or any person who earns their living from a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the particular knowledge and skills necessary to perform their specific role within that profession. In addition, most professionals are subject to strict codes of conduct, enshrining rigorous ethical and moral obligations. Professional standards of practice and ethics for a particular field are typically agreed upon and maintained through widely recognized professional associations, such as the IEEE. Some definitions of "professional" limit this term to those professions that serve some important aspect of public interest and the general good of society.