This purpose of this paper is to review and evaluate published literature on the biology and chemistry of lichens and their ecological, ethnopharmacological, pharmaceutical and therapeutic potential. A systematic method was used to gather literature on “the biology and chemistry of lichens and their ecological, ethnopharmacological, pharmaceutical and therapeutic potential.” A total of fifty-five research papers published between the years 1963 to 2022 were selected and utilized for this review. Tables were used to present the results. The subtopics were then chosen using a subjective method: lichens and their benefits/ importance. In this paper, eight (8) ecological functions and fourteen (14) pharmaceutical properties and therapeutic potentials were evaluated and presented. Lichen biology and chemistry and their roles in ethnopharmacological are also discussed. Additionally, lichens as pioneer and keystone species and their role as bioindicators to assess ecosystem health, sustainability and productivity was also addressed in this research. The published papers established that lichens have many benefits and importance, they are capable of synthesizing a range of chemicals that are beneficial to us and they are used in both traditional and pharmaceutical preparation of different treatments to combat many different diseases that affect human beings. More studies to investigate the uses of lichens should be done, especially in neotropics as there is a paucity of data and in this biodiversity rich region. Keywords: Lichens; Biology; Chemistry; Ecological; Ethnopharmacological; Pharmaceutical; Therapeutic potential.