The 100 krooni banknote (100 EEK) is a denomination of the Estonian kroon, the former currency of Estonia. Lydia Koidula (1843–1886), who was an Estonian poet and playwright, is featured on the front side of the banknote, which is why the 100 krooni banknote is often called a "Koidula".
A view of the north Estonian limestone shore is featured on the reverse side of the banknote. Before the replacement of the kroon by the euro, the 100 krooni banknote was the main everyday currency used by Estonians and was commonly dispensed by ATMs in Estonia as well as used for withdrawals or cashing checks. It can be exchanged indefinitely at the currency museum of Eesti Pank for €6.39.