The Data Theory major at UCLA joins the strength of UCLA’s Mathematics department with the innovation of its Statistics department to offer undergraduate students a world-class education in the foundations of Data Science. This capstone major is the first in the world, both in name and content. One key academic difference from the Data Science majors proposed by peer universities is the presence in our major of substantial upper division proof-based mathematics. The major is strong, perhaps stronger than some Masters degrees, in Machine Learning, which is at the core of Data Science. Most Data Science programs focus on teaching students the methods of data modeling, analysis, and engineering. What is missing is a rigorous understanding of the statistical and mathematical foundational concepts that underlie these methods. Without these, data scientists lack the understanding to deal with the plethora of problems they will face. UCLA’s Data Theory major fills this need.