The purpose of this work is to present several new retarded nonlinear integral inequalities which can act as powerful tools for studying qualitative properties such as existence, uniqueness, boundedness, stability, and asymptotics of solutions of nonlinear retarded differential and integral equations. These inequalities generalize some former famous inequalities on the subject. From applications perspective, two examples will be provided to demonstrate the strength of our inequalities in estimating the existence and boundedness of solutions for initial value problems of nonlinear retarded differential equations.