26 January – The French government and the Île-de-France Region merge their transit projects and sign an agreement that forms the Grand Paris Express.

20 March – The Grand Paris Express breaks ground at Aulnay-sous-Bois. Several thousand geotechnical probes will be required to accurately analyse the type of soil the metro will run through.

June – One year after preliminary work begins, the first civil engineering works for the Grand Paris Express start at the future site of the Fort d’Issy-Vanves-Clamart station.

6 February – Underground works begin. To mark the event, thousands of people come to see the first Grand Paris Express tunnelling machine in Champigny-sur-Marne.
 

29 October – The first Grand Paris Express tracks are lain at the Noisy-Champs station sidings.

November – Maiden voyage of the test train for the rolling stock that will run on Lines 15, 16, and 17.

April – The first ultra-low-carbon concrete voussoirs are installed and tested on Line 18. Société des grands projets spearheaded this innovation to reduce CO2 emissions during construction.

24 June - Line 14, extended to Orly airport, welcomes the first passengers.

14 May - The first trainset of Line 18 arrives at the Operations Center to begin testing