Obersiggenthal is a municipality located in the Limmat Valley, within the district of Baden, in the canton of Aargau, Switzerland.

Of the rest of the land, 19.6% is settled (buildings or roads) and the remainder (1.3%) is non-productive (rivers or lakes).

It consists of the villages of Nussbaumen, Kirchdorf and Rieden and the hamlets of Tromsberg, Ebnet and Hertenstein.

The blazon of the municipal coat of arms is Gules two Keys Argent in saltire crossed by the third double warded in Pale.

[9] The historical population is given in the following table:[3] The tithe barn at Kirchweg 14 is listed as a Swiss heritage site of national significance.

[12] From the 2000 census[update], 3,540 or 46.8% are Roman Catholic, while 1,927 or 25.5% belonged to the Swiss Reformed Church.