The purpose of this paper is to define and describe the 'Telos' or purpose of special education. We argue that special education has three main (tripartite) functions: (a) research, (b) a distinct system, and (c) special instruction. The overall Telos of special education is to provide an educational service to better serve students whose disabilities adversely affect their learning. Despite this overall Telos of special education, we see a more specific Telos for each function. In particular, the Telos of special education research should be based on the search for truth, whereas the Telos of the special education system focuses on promoting equality of opportunity, equity, and social justice. Last, the Telos of special education instruction is to optimize learning through specialized, individualized, and effective instruction, which is essential to achieve the overall Telos of special education. Current challenges to all three parts of special education's telos are discussed.