现实原则为佛洛依德的精神分析论，认定现实原则为人格结构中个人所遵从的原则，从精神的临床实验上，佛洛依德认为有两种不一样的精神反应程序：

「自我」介于「本我」与「超我」之间，「本我」遵守享乐原则，寻找即刻的满足，并且发泄原始的冲动，惟此冲动却限制于社会道德规范与现实法律，从而受到压抑，「自我」的主要功能则在依照现实原则，一方面在从现实中获取需求的满足，另外一方面不违规现实的约束，与环境保持良好的和谐。

In Freudian psychology and psychoanalysis, the reality principle (German:Realitätsprinzip) is the ability of the mind to assess the reality of the external world, and to act upon it accordingly, as opposed to acting on the pleasure principle.

Allowing the individual to defer (put off) instant gratification, the reality principle is the governing principle of the actions taken by the ego, after its slow development from a "pleasure-ego" into a "reality-ego": it may be compared to the triumph of reason over passion, head over heart, rational over emotional mind.