Illnau-Effretikon is a municipality in the district of Pfäffikon in the canton of Zürich in Switzerland.

Subsequently, the economic boom caused by the railway made Effretikon grow disproportionately until it had outgrown Illnau by the beginning of the 20th century.

Of the rest of the land, 17.2% is settled (buildings or roads) and the remainder (1.3%) is non-productive (rivers, glaciers or mountains).

As of 2007[update] 12.5% of the total municipal area was undergoing some type of construction.

It consists of the villages of Illnau, Effretikon (including Rikon), Ottikon and Bisikon as well as the hamlets of Agasul, Bietenholz, portions of Billikon, First, Horben, Kemleten, Luckhausen, portions of Mesikon and Oberkempttal.

Most of the population (as of 2000[update]) speaks German (84.9%), with Italian being second most common ( 4.3%) and Albanian being third ( 2.1%).

[8] The historical population is given in the following table:[6] The municipality of Illnau-Effretikon is served by two railway stations.

Effretikon railway station is on the Zurich to Winterthur main line and is served by Zürich S-Bahn routes S2, S3, S7, S8, S19 and S24.