The search for biopolymers to replace conventional fossil-based polymers is a focus of global interest in academia and industry. Studies on lignocellulosic biomass show that its components correspond to the most abundant biopolymer sources on Earth. Given this, lignin presents itself as an abundant and structurally rich macromolecule, capable of promoting the formulation of bio-based polymers. In addition to its wide range of sources and extraction methods, lignin has a complex chemical structure, which gives it a variety of functional groups. Characterizing lignin is of fundamental importance for a better understanding of its structure. This deals with the application of analytical techniques commonly used to characterize different lignins. Five types of lignin were subjected to FTIR, DSC, TGA, MEV-EDS, real density, porosimetry, BET, purity, ash, moisture, and nitrogen analysis. Lignin extraction was performed using the Klason method, and nitrogen was determined using the Kjeldahl method. Characterizations and compositional analysis described in this chapter were performed in order to provide valuable information on the chemistry, reaction pathways, thermochemical properties, and behavior of five types of lignin from three different sources. Thereby, the five lignins studied showed remarkable properties and composition, especially in terms of their purity levels, a fundamental parameter for their allocation as a raw material. Furthermore, these results can be used in technical and economic evaluations for harnessing lignins for several industrial purposes.