ALT We study international capital flows across 200 years. A major novelty is our analysis on official flows (government-to-government lending), which are routinely neglected in the vast literature on private capital flows. To trace official flows, we collect an encompassing new database of 1.1 million cross-border loans, grants and guarantees from foreign governments, central banks, and multilateral organizations over the period 1790-2020. The size of official cross-border flows often exceeds total private flows, especially during wars and financial crises. Official flows are counter-cyclical, surging when private capital flows retreat, and acting as a counterweight during economic downturns and disasters. Time and again, official international lending has helped avert military defeat or financial collapse abroad. We conclude that official finance is a crucial but underappreciated pillar of the international financial system.