2013 Reprint of 1956 Second Edition. Full facsimile of the original edition, not reproduced with Optical Recognition Software. "Foundations of the Theory of Probability" by Andrey Nikolaevich Kolmogorov is historically important in the history of mathematics. It is the foundation of modern probability theory. The monograph appeared as "Grundbegriffe der Wahrscheinlichkeitsrechnung" in 1933 and build up probability theory in a rigorous way similar to what Euclid did with geometry. With this treastise Kolmogorov laid the foundations for modern probability theory and established his reputation as the world's leading expert in this field.