Until January 1, 2007 Tranekær municipality was a municipality (Danish, kommune) in the former Funen County on the island of Langeland in south-central Denmark. The municipality included the islands of Siø, and covered an area of 107 km². It had a total population of 3,467 (2005). Its last mayor was Jørgen Nielsen, a member of the Venstre (Liberal Party) political party.
The main town and the site of its municipal council was the town of Tranekær. To the west are the waters of the Great Belt and to the north and east are the waters of the Langeland Belt (Langelandsbælt).
The municipality was created in 1970 due to a kommunalreform ("Municipality Reform") that combined a number of existing parishes:
Tranekær municipality ceased to exist as the result of Kommunalreformen ("The Municipality Reform" of 2007). It was merged with Rudkøbing and Sydlangeland municipalities to form the new Langeland municipality. This created a municipality with an area of 290 km² and a total population of 14,223 (2005). The new municipality belongs to Region of Southern Denmark.