What is the name of the interest rate that U.S. banks charge each other for overnight loans of reserves?

The interest rate U.S. banks charge one another for overnight loans of reserves is called the federal funds rate.

Banks and other eligible depository institutions hold reserve balances in accounts at Federal Reserve Banks. One institution may have more reserves than it needs for payments or liquidity, while another may need to borrow. The interest rate negotiated in this overnight federal funds market is the federal funds rate.

The Federal Open Market Committee sets a target range for the rate and uses monetary-policy tools to keep the market rate near that range. Changes in the rate influence other short-term borrowing costs and can affect spending, investment, employment, and inflation. The effective federal funds rate is a market measure, not simply a rate posted by one bank.

LIBOR was a benchmark for certain wholesale loans and has been phased out in major markets. The prime rate is what banks commonly charge their strongest commercial borrowers, while the discount rate applies to Federal Reserve lending through the discount window.