Background/Objectives: Prostate cancer (PCa) outcomes vary significantly across risk groups. In early-stage localized PCa, the functional outcomes following radical prostatectomy (RP) can be severe, prompting increased interest in focal therapy, particularly High-Intensity Focused Ultrasound (HIFU). This study is to summarize the current clinical trials of HIFU on PCa. Methods: We reviewed clinical trials from major databases, including PubMed, MEDLINE, Scopus, and EMBASE, to summarize the current research on HIFU in PCa treatment. Results: The literature highlights that HIFU may offer superior functional outcomes, particularly in continence recovery, compared to RP and radiation therapy. However, the oncological efficacy of HIFU remains inadequately supported by high-quality studies. Focal and hemigland ablations carry a risk of residual significant cancer, necessitating comprehensive patient counseling before treatment. For post-HIFU monitoring, we recommend 3T magnetic resonance imaging (MRI) with biopsy at 6 to 12 months to reassess the cancer status. Biochemical recurrence should be defined using the Phoenix criteria, and PSMA PET/CT can be considered for identifying recurrence in biopsy-negative patients. Conclusions: Whole-gland ablation is recommended as the general approach, as it provides a lower PSA nadir and avoids the higher positive biopsy rates observed after focal and hemigland ablation in both treated and untreated lobes. Future study designs should address heterogeneity, including variations in recurrence definitions and surveillance strategies, to provide more robust evidence for HIFU’s oncological outcomes.