Hospital-acquired infections (HAIs) burden Saudi Arabian healthcare, affecting 15-20% of patients amid Hajj pilgrim surges and Vision 2030 goals for a 30% reduction by 2030. This prospective cohort study evaluated a multimodal infection prevention and control (IPC) bundle's impact across five tertiary hospitals in Riyadh, Jeddah, and Dammam. From January 2024 to December 2025, 12,500 patients (1.065 million patient-days) and 1,200 healthcare workers underwent active HAI surveillance per CDC NHSN definitions. Interventions included hand hygiene campaigns (WHO 5 Moments), risk-stratified PPE, early PCR screening, hydrogen peroxide vapor disinfection, and electronic audits. Outcomes assessed pre-/post HAI rates (CLABSIs, CAUTIs, VAPs, SSIs), compliance (n=10,000 observations), MDRO swabs (n=5,000), and logistic regression for predictors. Baseline HAI rate was 2.2/1,000 patient-days, declining 46% to 1.2 post-intervention (p<0.001). Device-associated HAIs reduced 45-48%; hand hygiene compliance rose from 62% to 92%, PPE from 63% to 93%, and MDRO contamination from 28% to 6% (79% clearance). High compliance protected against HAIs (OR=0.42, 95% CI 0.35-0.50). Length of stay shortened 1.8 days, projecting SAR 45 million savings.The IPC bundle achieved superior, sustained HAI reductions exceeding expectations, validating CBAHI-aligned protocols for Saudi contexts and informing GCC policy.