Transnational corporations play a major, but poorly constrained, role in reallocating global water resources. Here, we couple high-resolution, company-specific trade data with hydrological and crop models to estimate the virtual water trade of the top 10 transnational corporations that trade Brazilian soy. We identify 4429 virtual water flows connecting 1620 Brazilian municipalities with the top-10 soy importing countries and find that the total virtual water flow increased from 43 billion m3 to 100 billion m3 between 2004 and 2018. We find that the largest soy traders displace on average twice as much virtual water as top-importing countries, excluding China. For example, in 2018 Bunge Limited exported 15 Gm3, almost tripling the Netherlands's virtual water import (the second largest importer at about 5 Gm3). Our findings highlight the importance of transnational corporations for achieving water stewardship and sustainable supply chains to support water resource security at municipal and international scales.