The article deals with the concept of public order (public policy) in national law systems, including international private law (conflict of laws). The essay focuses on public policy (public order) regulated by the Rome Convention of 1980 on the Law Applicable to Contractual Obligations and Regulation (EC) No 593/2008. The notion “public order” or “ordre public” is to be distinguished from “ordre public interne” and “ordre public international.” There is also a problem of terminology. Some authors have identified “imperative,” “peremptory,” “mandatory,” “jus cogens” and “public order norms.” The last chapter refers to the peremptory norms (jus cogens) in international public law.