A designer is one who deliberately shapes a form within a particular context to produce a desired effect or fitness for a purpose. The forms shaped by the designer can be concrete, manifesting as physical artifacts, or be as abstract as a set of symbols or an agreement between entities.

A professional designer is disciplined in the art of interpreting will, depicting a context, and then defining a form to fit that context. Designers often act as agents on behalf of other entities for this purpose, mediating the intent of the client and the capabilities of the production team, as well as supervising production, alone or in tandem with a project manager.

In The Design of Everyday Things, Donald Norman argues that everyone is a designer insofar as all people continually shape their environment as an integral part of their behaviour. Others, such as Bill Buxton, assert that the title should be reserved for the aforementioned professionals.

Designers of objects that are markedly immobile, long-lived and potentially very expensive are traditionally called architects.