An iron law is a law or principle that is meant to be both indisputable and unavoidable, and may refer to:

• Iron law of population, from Thomas Malthus' An Essay on the Principle of Population (1798)
• Iron law of wages, from Ferdinand Lassalle's Subsistence theory of wages (mid 19th century)
• Iron law of oligarchy, from Michels' Political Parties
• Iron law of prohibition, from Cohen's How the Narcs Created Crack
• Iron Law of Bureaucracy, from Jerry Pournelle.