This paper introduces the concept of frugal data science as a topic of data science and lays its functional principles. Frugal data science is an extension of frugal science, which aims at simple, low-cost, yet efficient, and effective solutions into the field of data science. The state of the discipline of data science calls for such a concept of frugality, due to many barriers, limitations, and challenges encountered in real-world data science projects. To this end, the paper illustrates with three case studies how such limitations can be overcome through the introduced concept of frugal data science.