The paper proposes GDP-contingent loans (GCLs) as a novel war-financing mechanism for Ukraine, linking repayments to economic performance (e.g., real GDP growth) and thus balancing donor burden and sustainable repayment. GCLs are inspired by income-contingent loans used in higher education; featuring a repayment-free threshold (e.g., pre-war GDP levels) and repayments as a proportion of each year’s GDP growth (e.g., 35% or 50%). Simulations comparing GCLs and standard loans (SLs) under Ukraine’s context (e.g., $100 billion loan, 2025–2045) show GCLs prevent debt traps and stagnation by pausing repayments during recessions and pre-recovery phases, unlike SLs, which impose fixed burdens regardless of economic conditions. Incorporating fiscal multipliers highlights GCLs’ superiority, as SLs’ early repayments reduce GDP growth (e.g., $232 billion by 2049 vs. $301 billion under GCLs), while GCLs’ countercyclical design supports recovery. Our analysis suggests that a GCL is a valuable debt-management instrument that would benefit both lenders and Ukraine (or any crisis-struck country); offering lower default risk, better income smoothing, and greater political acceptability.