Altbier (German: [ˈaltˌbiːɐ̯] ^ⓘ, lit. 'old beer') is a style of beer brewed in the Rhineland, especially around the city of Düsseldorf, Germany. It is a copper coloured beer whose name comes from it being top-fermented, an older method than the bottom fermentation of lagers.

Altbier is usually a dark, copper colour. It is fermented at a moderate temperature using a top-fermenting yeast—which gives its flavour some fruitiness. Because Altbier is then matured at a cooler temperature, its flavour is more akin to lager beer styles than is the norm for top-fermented beers (such as British pale ale). It generally has an ABV between 4.3% and 5.5%.

The first producer to use the name Altbier—to contrast its top-fermenting beer with the bottom-fermenting kinds—was the Schumacher brewery of Düsseldorf, that opened in 1838. Mass-market brewers of Altbier include Diebels and the Radeberger Gruppe under the brands Schlösser Alt and Hansa Alt. These are complemented by small breweries in Düsseldorf and other nearby cities.

Some Altbier breweries have a tradition of producing a stronger version, called sticke alt, coming from a local dialect word meaning "secret". Originally made as a special reserve beer intended for the brewers' own consumption, today it is generally a seasonal or special occasion brew.

There exists a regional rivalry between the drinkers of Altbier in the Düsseldorf area and the drinkers of Kölsch beer in the Cologne (Köln) area.

A beer variety associated with the Lower Rhine region, Altbier is especially found in Düsseldorf, Krefeld, and Mönchengladbach.

There are seven bars in Düsseldorf which brew Altbier on the premises:

Füchschen, Uerige, Schlüssel and Kürzer are all brewed and sold in the Altstadt (Old Town). Schumacher is between the Altstadt and the main train station (Hauptbahnhof), although it also has a pub in the Altstadt, Im Goldenen Kessel, across the street from Schlüssel.