Aulnay-sous-Bois (French pronunciation: [o(l)nɛ su bwɑ] ⓘ) is a commune in the Seine-Saint-Denis department in the Île-de-France region in the north-eastern suburbs of Paris, France.

Route nationale 2 passes through the heart of the commune from west to east with the N370 coming from the south-east along the eastern border to join the N2.

Its mission was to provide shelter for workers and managers for a new Citroën plant to be located a few hundred metres away.

The city is served by: The commune is traversed by the main railway line from Paris to Soissons, Laon, and Hirson which serves the Aulnay-sous-Bois station where all buses and semi-direct services of (Roissy and Mitry-Mory) and the Transilien Paris to Crépy-en-Valois (connecting with TER Villers to Cotterêts/Soissons/Laon) stop and it is the terminus of the line.

Since November 2006, the classic commuter train the Ligne des Coquetiers (The Egg-cups line) between Aulnay-sous-Bois to Bondy has been replaced by a Tram-train that takes the same route and allows connection to the and .

In 2023 a station on line 16 in the Grand Paris Express project is planned north of the commune on the embankment of the former N2 road.

The commune was renamed Aulnay-sous-Bois (i.e. "Aulnay under the woods") on 5 January 1903 in reference to the ancient Forest of Bondy.

Other nearby commune names (Clichy-sous-Bois, Les Pavillons-sous-Bois, and Rosny-sous-Bois) also refer to the same forest.

Between the 4th and 2nd centuries BC, farmers living around a "villa" belonging to Sabinus - the Savigny Farm.

Two places independent from the parish of Saint Sulpice were Savigny and Nonneville which were attached to the current village.

The lord Jacques Coitier passed succession to his heirs through his nephew to the Gourgues family.

The Canal de l'Ourcq was dug during the Napoleonic period to facilitate relations with Paris.

On 15 August 1838 a postal boat service was started on the Canal de l'Ourcq from Paris to Meaux.

In 1896 the municipal council was mostly made up of inhabitants of Parc but undertook the development of the entire community of Aulnay.

Tempted by the greenery on the outskirts of Paris, Parisians bought land and transformed the place into a holiday and residential area.

In September 1914 Aulnay was saved from German military occupation by the counter-offensive during the First Battle of the Marne.

There is even a political divide, with Aulnay-Nord Canton sending a Socialist representative (Gerard Segura) to the Council-General for the Seine-Saint-Denis Department, but Aulnay-Sud a conservative (Jacques Chaussat).

[15] The Centre for Strategic Analysis conducted a study on the city: the extract below tends to reflect a bad reputation, not necessarily deserved in all its aspects.

[18] The city had good growth due to companies like L'Oréal and PSA Peugeot Citroën being located there.

[23] The plant has subsequently produced various Citroën and Peugeot models and has on occasion hit the headlines as a focus of industrial strife.

On 12 July 2012 PSA Peugeot Citroën announced that it will permanently close the Aulnay-sous-Bois plant due to overcapacity.

The repository, established in 2002,[25] is not open to the public although members of Citroën enthusiasts' clubs and other important visitors are occasionally granted access to it.

The commune has a number of buildings which contain items registered as historical objects: The commune has one religious building that is registered as a historical monument: Other churches contain items registered as historical objects: Aulnay has 153 hectares of green space of which these are the main ones: In 1981 and 1982, Aulnay-sous-Bois was a stage town for the 68th and 69th Tour de France during the 10th stage (Le Mans-Aulnay-sous-Bois) in 1982 and for the 20th stage in 1982 (Sens-Aulnay-sous-Bois).

Every winter an outdoor skating rink (600 metres square in 2006–2007) is installed at the Vieux Pays Farm.

Every Easter Monday there is a Spring Fair that combines antiques, a flea market, and a garage sale.

It unites for one week different theatrical companies of children, adolescents, and adults who present their creations on stage.

[55] In early June there is the Festival of Towns in Flower and Cycling in Gainville (Parc des Cygnes) Park.

In the afternoon there is a parade from the Vieux Pays Farm and a concert in the Pierre Scohy gymnasium.

The Festival of the Canal de l'Ourcq is held in mid-June between the Pavilions-sous-Bois port and the Jardins Perdus Gateway.

The traditional Festival of the Tree takes place for two days in early November at Dumont Park.