Each year, around 500,000 children under 5 die from diarrhea, making it the third-leading cause of death in this age group. More than 80 percent of these deaths are attributable to unsafe drinking water. Drinking water can be made safe through dilute chlorine solution, but take-up of this technology has been low. Previous work has shown that free community-wide provision of dilute chlorine solution through “dispensers” – reservoirs of chlorine solution at water sources that make chlorination easy and free – increases take-up of chlorination. However, it has remained unclear whether this increase also translates into reduced mortality. Here we show that four years of community-wide provision of dilute chlorine solution in rural Kenya reduces all-cause under-5 mortality by 1.4 percentage points (95% CI: 0.3 pp, 2.5 pp), a 63% reduction relative to control. We estimate that at USD 25 per DALY averted, free provision of chlorine solution is twenty times more cost-effective than the WHO “highly cost-effective” threshold.