The €STR (euro short-term rate) is the euro area’s overnight interest rate: it reflects how much it costs banks to borrow unsecured money for a single night. It is computed and published every day by the European Central Bank from real transactions, and has effectively replaced the old Eonia. It is the “purest” reference for the very short-term cost of money in the euro area, and moves very close to the ECB’s deposit rate.