Othmarsingen is a municipality in the district of Lenzburg in the canton of Aargau in Switzerland.

Mesolithic siliceous rock objects and tools and Hallstatt era graves indicate that the Othmarsingen area was prehistorically occupied.

The court that constituted Othmarsingen also included, Ammerswil, Dintikon and Brunegg in 1539 and was under a bailiff.

[3] Othmarsingen has an area, as of 2009[update], of 4.73 square kilometers (1.83 sq mi).

Of the rest of the land, 1.15 km2 (0.44 sq mi) or 24.3% is settled (buildings or roads), 0.02 km2 (4.9 acres) or 0.4% is either rivers or lakes.

The blazon of the municipal coat of arms is Azure a Church Argent roofed Gules on a Bridge masoned.

Most of the population (as of 2000[update]) speaks German (87.2%), with Italian being second most common ( 2.2%) and Turkish being third ( 2.1%).

[8] The age distribution, as of 2008[update], in Othmarsingen is; 220 children or 9.4% of the population are between 0 and 9 years old and 334 teenagers or 14.3% are between 10 and 19.

[10] About 51.6% of the total households were owner occupied, or in other words did not pay rent (though they may have a mortgage or a rent-to-own agreement).

[8] The historical population is given in the following table:[3] The village Reformed church is listed as a Swiss heritage site of national significance.

[8] From the 2000 census[update], 673 or 31.8% were Roman Catholic, while 967 or 45.7% belonged to the Swiss Reformed Church.

It was open a total of 90 days with average of 2 hours per week during that year.

[16] As of December 2024[update], Othmarsingen railway station is a stop of Zurich S-Bahn services S11 and S42.