Rationalism is a philosophical position, theory, or view that reason is the source of knowledge.

Rationalism may also refer to:

• Rationalism (architecture), a term applied to a number of architectural movements
• Rationalism (international relations), a political perspective on the international system
• Rationalism (theology), philosophical Rationalism applied in theology
• Critical rationalism, an epistemological philosophy advanced by Karl Raimund Popper
• Economic rationalism, an Australian term in discussion of microeconomic policy
• Pancritical rationalism, a theory by William Warren Bartley developed from panrationalism and critical rationalism

• Rational (disambiguation)
• Rationale (disambiguation)
• Rationality
• Rationalization (disambiguation)