A beamsplitter is a common optical component that partially transmits and partially reflects an incident light beam; this splitting usually occurs in unequal proportions. This chapter explains the basic principles that govern light passing through a beamsplitter, and presents various types of beamsplitters and their applications. Light passing through beamsplitters is governed by the laws of light. The light beam output components can be arranged exiting the beamsplitters either parallel or perpendicular to the input light. Standard cube beamsplitters consist of matched pairs of right angle prisms cemented together along their hypotenuses. Cube beamsplittes are available in two categories: polarizing and non-polarizing. Cube beamsplitters are available in three types: broadband hybrid, broadband dielectric, and laser-line non-polarizing. Rectangular polarizing beamsplitters perform the same function as cube beamsplitters. The chapter presents several experimental cases that demonstrate the principles of the light passing through beamsplitters in optical fibre devices.