Unterengstringen is a municipality in the district of Dietikon in the canton of Zürich in Switzerland, located in the Limmat Valley (German: Limmattal).

Of the rest of the land, 33.2% is settled (buildings or roads) and the remainder (3.3%) is non-productive (rivers, glaciers or mountains).

As of 2007[update] 29.3% of the total municipal area was undergoing some type of construction.

Most of the population (as of 2000[update]) speaks German (87.4%), with Italian being second most common ( 3.0%) and French being third ( 1.6%).

In the 2007 election the most popular party was the SVP which received 45.3% of the vote.