The subject of fluid mechanics is filled with abstract concepts, mathematical methods, and results. Historically, it has been a challenging subject for students, undergraduate and graduate. In most institutions, the introductory course in fluid mechanics is accompanied by a laboratory course. While institutional philosophy and orientation vary around the world, the goal of that laboratory is to strengthen students’ understanding of fluid mechanics using a variety of laboratory exercises (Feisel & Rosa, 2005). The literature has identified six basic functions of experimental work. Indeed, the report of the Laboratory Development Committee of the Commission on Engineering Education identified six key functions and objectives of the instructional laboratory (Ernest, 1983): a. Familiarization b. Model identification c. Validation of assumptions d. Prediction of the performance of complex systems e. Testing for compliance with specifications f. And exploration for new fundamental information. The report states that “The role of the undergraduate instructional laboratory is to teach student engineers to perform these six functions. Hence the primary goal of undergraduate laboratories is to inculcate into the student the theory and practice of experimentation. This includes instrumentation and measurement theory.” (Ernst, 1983). The wind tunnel is one such instrument. This chapter focuses on the measurement theory on which the wind tunnel is based and presents examples of its use in the undergraduate fluid mechanics laboratory at Indiana University-Purdue University Fort Wayne, Fort Wayne, Indiana, USA. The remainder of the chapter is organized in the following manner: 1. Basic concepts discuss definitions, classifications, and various uses of wind tunnels. 2. Fundamental Equations present the equations that are used as foundations for the theory and application of wind tunnels. 3. Applications of wind tunnels in teaching fluid mechanics present nine different examples that are used in our laboratory to teach various aspects of fluid mechanics and its uses in design, testing, model verification, and research. 4. References list all cited works in alphabetical order.