Toll-like receptors (TLRs) have attracted interest due to their role in detecting pathogens and regulating the pro-inflammatory immune response. To date, 10 functional TLRs (TLR1-10) have been detected in humans. These TLRs control diverse immunological and embryonic development processes to maintain immune homeostasis and healthy fetal growth and development. They recognize diverse pathogen-associated molecular patterns (PAMPs) and death/damage-associated molecular patterns (DAMPs) to maintain immune homeostasis via regulating diverse immunological processes. This book discusses TLRs from their evolution to immunological functions governing infection and inflammation pathogenesis, cancer immunology, and their interactions with other pro-inflammatory molecules generated during inflammation pathogenesis. It is a must-read for researchers interested in TLR biology and the role of TLRs in infection, immunity, and cancer.