Cognitive distortions are specific, systematic errors in thinking that lead to inaccurate perceptions (e.g., catastrophizing, overgeneralization). Irrational beliefs, as described in Rational Emotive Behavior Therapy (REBT), are deeply held, global, and unrealistic assumptions about oneself, others, or the world (e.g., "I must be loved by everyone to be worthwhile"). While both are central to cognitive behavioral therapies, cognitive distortions are seen as habitual faulty thought patterns, whereas irrational beliefs are more generalized and fundamental in shaping one's worldview.
Reference: Helwig, A. A. (2020). CPCE Study Guide and Review; Corey, G. (2017). Theory and Practice of Counseling and Psychotherapy (10th Edition).