The Free State of Bottleneck (German: Freistaat Flaschenhals) was a short-lived quasi-state that existed from 10 January 1919 until 25 February 1923.

The French and American zones did not meet entirely, leaving a narrow gap on the eastern side of the Rhine containing the Wisper valley, the towns of Lorch and Kaub, and villages of Lorchhausen, Sauerthal, Ransel, Wollmerschied, Welterod, Zorn, Strüth and Egenrod.

Surrounded by the two Allied bridgeheads, the Rhine to the south-west and no roads nor railways to speak of towards the north-east, this tiny region was effectively cut off from the rest of Germany and subsequently separated from the administration of the Weimar Republic.

Owing to the circular nature of the Allied bridgeheads, this enclosed territory took on the shape of a bottleneck, hence the name that was given to the microstate, when it was declared on 10 January 1919.

There were no roads connecting the Bottleneck to unoccupied Germany, trains were not permitted to stop there, and air or river transportation was impossible.