 This article has three parts. After giving an overview of the common features of Neo-Kantians, section 2 is devoted to the Marburg School, and section 3 to the Southwest (SW) School. The Neo-Kantians were systematic and comprehensive philosophers, writing on nearly every area of philosophy. Instead of attempting to cover all areas of their thought, this article will focus on the areas of their philosophies that were most central to their thought, and that were most influential on their contemporaries and successors. Accordingly, each section begins with each school’s conception of philosophy (sections 2.1 and 3.1), moves on to their theory of knowledge (2.2 and 3.2), and ends with the philosophy of the special sciences most characteristic of each school (2.3 on Marburg philosophy of physics, and 3.3 on SW philosophy of history). (Three supplementary documents cover philosophies of logic, psychology, and mathematics in the Marburg School.)