The design and implementation of random number generators (RNGs) have been widely studied during the last years to improve applications that require random sequences. The RNGs can be classified as true (TRNGs) or pseudo (PRNGs), and either or both can be designed by using different algorithms or hardware. This chapter shows the basics of PRNGs and introduces the ways they are implemented by using chaotic maps, chaotic systems, and fractional-order chaotic oscillators. The goal of the book is devoted to provide guidelines for the block descriptions of chaotic maps and systems, their Verilog descriptions, and their FPGA implementation. This chapter provides a general overview of the application of RNGs, their design using chaotic systems, and their hardware implementations.