This chapter reviews the available optical flow (OF) sensing techniques and their applications in unmanned aerial vehicle (UAV) navigation and control. It introduces an intelligent OF sensor fusion technique for terminal-phase landing, which is also presented in the work. The chapter also introduces a dynamic model of the flybarless helicopter. It surveys OF algorithms and their applications in the field of UAV control and estimation. The chapter presents a quantitative evaluation of different OF algorithms. It also presents the intelligent OF sensor fusion design. The chapter demonstrates the simulation results of the intelligent state estimation algorithm. It overviews the OF sensing concepts and explores how the concepts can be used to measure positional changes in terms of real-world distances. The chapter presents an existing OF algorithms used in UAV navigation and positioning applications. It summarizes state-of-the-art sensors and approaches used to provide accurate OF estimates.