Flaach is a municipality in the district of Andelfingen in the canton of Zürich in Switzerland.

Flaach is first mentioned in 1044 as Flacha, though the only surviving copy of the document dates from 1347.

Of the rest of the land, 8.2% is settled (buildings or roads) and the remainder (6.2%) is non-productive (rivers, glaciers or mountains).

Schloss Flaach is a Swiss heritage site of national significance.

[4] The historical population is given in the following table:[3] The seventh Chief Apostle of the New Apostolic Church, Richard Fehr, was born in Flaach on 15 July 1939.