The Amper, called the Ammer upstream of the Ammersee, through which it runs, is the largest tributary of the Isar in southern Bavaria, Germany.

Over a distance of around 100 km, the Amper crosses four natural areas: the steep old and young moraines, the flat gravel plain and the Danube-Isar hill country.

A little before that, the Alte Ammer branches off to the left, which after a short run is absorbed by the longer but usually less watery Rott, which also flows into the Ammersee.

The first tributary of the Ammer is shortly after the connection of the outflows from the Große Ammerquellen with the Linder is the approximately 7 kilometers long near Kohlbach.

Larger tributaries in the further course to the Ammersee are the Angerbach near Weilheim in Upper Bavaria, the Grünbach near Wielenbach and the Kinschbach near Pähl, all of which flow into them from the right.

Since the middle of the 19th century, the natural course of the Ammer and Amper has been significantly changed by flood protection and the construction of power plants – with far-reaching consequences for the native flora and fauna.

After the opening of the railway line between Munich and Herrsching, the number of passengers on the water sank so much that the costs of keeping the section navigable made operation uneconomical; the ship connection from Grafrath to Stegen had to be stopped.

It was popularly known as the "Mooskuh" because the entire route between Grafrath and the Ammersee ran through the Ampermoos and its beep resembled the call of the bittern.

It served to supply the 23-kilometer-long line between Murnau and Oberammergau belonging to the Lokalbahn Aktien-Gesellschaft, which started the first scheduled electric train service in 1905.

A number of other run-of-river power plants along the river system with regional economic importance emerged in this way, mostly up to the First World War.

Hydropower plants require a consistently high water level so that energy generation does not come to a standstill in months with little rainfall.

In addition to a number of interesting cities along the Ammer and Amper rivers such as Weilheim, Fürstenfeldbruck, Dachau and Moosburg, the Ammersee in particular is of touristic importance.

Long stretches of the river are lined with cycle paths that allow tours from the Alps to the mouth of the Amper at Moosburg an der Isar.

Driving on the Ammer and Amper with canoes or similarly manoeuvrable boats is possible over almost the entire route, but not allowed all year round.

[2] During the bird breeding season (1 March to 15 July), driving on the Amper from Stegen to Grafrath and between Schöngeising and Fürstenfeldbruck is prohibited.