As others said, U.S. Treasury bonds are widely held across the globe. But the largest single holder is actually the U.S. federal government itself, which holds

As others said, U.S. Treasury bonds are widely held across the globe. But the largest single holder is actually the U.S. federal government itself, which holds about 20% of the total debt as “intragovernmental” debt. These are real, legally binding financial obligations to federal agencies, most famously to Social Security.