Ancienville is located some 10 km east by south east of Villers-Cotterets and 25 km south-west of Soissons. The commune can be accessed by the D973 road from Villers-Cotterets in the north-west continuing west through the heart of the commune north of the village to Chouy. The D1370 runs south from the D973 and passes through the village continuing south to Noroy-sur-Ourcq. The commune is partly farmland with forests in an arc from the south-west to the north-east.
La Savieres river flows south forming the western border of the commune and continues to join the Ourcq river near Silly-la-Poterie.
In 2010, the commune had 73 inhabitants. The evolution of the number of inhabitants is known through the population censuses conducted in the town since 1793. From the 21st century, a census of municipalities with fewer than 10,000 inhabitants is held every five years, unlike larger towns that have a sample survey every year.[Note 1]
^At the beginning of the 21st century, the methods of identification have been modified by law No. 2002-276 of 27 February 2002 , the so-called "law of local democracy" and in particular Title V "census operations" which allow, after a transitional period running from 2004 to 2008, the annual publication of the legal population of the different French administrative districts. For municipalities with a population greater than 10,000 inhabitants, a sample survey is conducted annually, the entire territory of these municipalities is taken into account at the end of the period of five years. The first "legal population" after 1999 under this new law came into force in 1 January 2009 and was based on the census of 2006.