Is it true that a treasury security is risk free?

While U.S. Treasury securities are often considered "risk-free" in terms of default risk, as they are backed by the full faith and credit of the U.S. government, they are not entirely free of risks. Investors still face interest rate risk, where the value of the securities may decline if interest rates rise, and inflation risk, as the purchasing power of future payments may be eroded by inflation. Therefore, while they are among the safest investments available, they are not completely devoid of risk.