The economic relationship between the United States and the European Union (EU) is unique as it is based on investment rather than on trade. Yet, in a sense they have no investment relationship: while the United States has investment treaties with most of the EU’s 27 member states, it has none with the EU itself. On one hand, the substantial investment across the Atlantic may indicate no legal framework is needed between them. And the political controversy surrounding investment negotiations in both the United States and Europe could argue against starting a negotiation that could raise acrimony rather than the amity it’s meant to create. But a Transatlantic Investment Agreement, if done properly, would be useful as it could remove lingering doubts about U.S. and EU openness to foreign investment, liberalize new areas for investment between them, and strengthen international investment law, thus helping improve business climates in other countries. This paper lays out a path for the United States and European Union to recognize, consecrate, and even celebrate this unique economic relationship.