In recent years, the successful use of tumor-infiltrating lymphocyte (TIL) therapy to treat melanoma not only culminated in a landmark Food and Drug Administration approval, but has also fueled the emergence of a new, rapidly growing field in TIL cellular immunotherapy surrounding novel enhancements in TIL design, refined manufacturing strategies to enrich for more potent TIL populations, as well as numerous clinical trials now investigating TIL therapy in additional solid tumor types beyond melanoma. This review provides a summary of the latest advances in TIL therapy and what lies ahead for the field. The first section explores several solid cancers that demonstrate the greatest potential for future indications of TIL therapy. The second section provides insight into the promising innovations for designing the next generation of TIL with greater specificity, persistence, safety, and function.