'Walfisch' was a German unrealised plan to land a seaplane on a lake in Éire (Irish Free State), possibly with planning aid from the German-based Irish Republican Army agent Frank Ryan (1940).

All planning for the operation, which was the brainchild of the Abwehr’s Abteilung II sabotage and special purposes department and whose objective is not known, had been abandoned by July 1940.