Lohmar (German pronunciation: [ˈloːmaʁ] ^ⓘ; Ripuarian: Luhme) is a municipality and a town in the Rhein-Sieg district, in North Rhine-Westphalia, Germany.

Lohmar is located about 20 km east of Cologne and 15 km north-east of Bonn in the Bergisches Land area. Because it is only 20 minutes by car to Cologne or Bonn, Lohmar is a popular place for commuters.

The municipality of Lohmar is divided into two parts: Lohmar itself and Wahlscheid 7 km to the north. About a third of the total population lives in Wahlscheid (a separate municipality until 1969). In total Lohmar comprises 30 districts. The most important are Lohmar itself (est. population approx. 9500), Donrath (2200), Heide (2100) and Birk (1400) in the south, as well as Wahlscheid (3200), Neuhonrath (2000), Honrath (1500) and Agger (1000) in the north.

Lohmar, Donrath, Wahlscheid, Neuhonrath and Agger are located in the Agger valley, the other villages in the uplands.

Lohmar was first mentioned as a donation of archbishop Sigewid to the church of Cologne. A farmyard in Lomereis mentioned.

Lohmar is also mentioned on the Arc de Triomphe in Paris as a place of Napoleon's visit. While his inspection of the army positioned in the Rhineland in 1811 he lived in Schloss Auel in Lohmar.

The town council consists of 40 members. The current breakdown after the local elections held on 13 September 2020 is as follows:

The CDU and Grünen govern the town as a coalition.