Rotismühle, Historic watermill in Leutkirch im Allgäu, Germany.

Rotismühle is a former castle mill in the Rotis hamlet of Leutkirch im Allgäu, first documented in 1414. Its four water wheels once drove a grain mill and sawmill; in 1924/25 Anton Bertele replaced them with two Francis turbines, one later swapped for an Ossberger turbine in 1950. The powerhouse's north wall was glazed in 1982 to Otl Aicher's plans, and a 20-by-10-metre house replaced the sawmill.

First documented in 1414 as a castle mill in Rotis, the Rotismühle ground grain with four water wheels and ran a sawmill until the 1920s. In 1924/25 miller Anton Bertele replaced the wheels with two Francis turbines fed by a 150-metre power canal from the Hofser Ach; one was swapped for an Ossberger turbine in 1950. Milling was deregistered in 1960 and the sawmill closed in 1970. Otl and Inge Aicher-Scholl bought the site in 1971, and from 1984 to 1991 it housed the Rotis Institute for Analog Studies.

The name Rotis comes from the hamlet, and the mill gave its name to Otl Aicher's 1988 Rotis typeface, developed while he ran his studio here. Aicher and Inge Aicher-Scholl bought the site in 1971, and their 'rotis büro' became jokingly known as the 'autonomous republic of rotis'. From 1984 to 1991 the Rotis Institute for Analog Studies trained designers in visual identity here.

The site is private property, so visits depend on the owners' consent; the powerhouse is best viewed from outside along the Hofser Ach. The 150-metre headrace canal, weirs and two turbines can be traced on foot. Heavy rain in 2010, 2015 and 2016 damaged the river structures, so paths near the water may be affected.

The mill stopped grinding grain in 1960 and its sawmill closed in 1970; since 1924/25 two Francis turbines, one replaced in 1950 by an Ossberger turbine, have generated electricity from the Hofser Ach. Until 1994 it ran as an isolated plant with no public grid. Otl Aicher, who bought the site in 1971, named his typeface "Rotis" after it.