The Triffin Dilemma (or Triffin Paradox) is a fundamental problem in international economics that explains why the issuer of the world's primary reserve currency faces an inherent conflict.
The world needs a growing supply of the reserve currency (like the US dollar) for international trade and financial transactions.
The main way to supply this currency globally is through trade deficits — the reserve currency country (like the US) runs trade deficits, sending dollars abroad.
However, persistent trade deficits can harm the issuing country's economy and erode confidence in the currency. This creates a dilemma: supply the world's liquidity needs at the cost of domestic economic health, or prioritize domestic stability and starve the world of needed reserves.