The book "Retarded Optimal Control Problem: Applications in Eco-Epidemiology" offers a comprehensive analysis of optimal control theory, taking into account time delays in biological and ecological systems. It highlights the challenges arising from the assumption that future states of a system are determined solely by present states and discusses the necessity of incorporating past states into modeling. By applying mathematical models that consider time delays, it aims to provide a deeper understanding of the dynamics of complex systems across various disciplines, including biology and epidemiology. The book is intended for professionals and students engaged with mathematical models and their applications in the natural sciences.